Onsim Reviews 64

Excellent customer support; extremely helpful and patient. Great product at a great price! Highly recommend

Great service after moving a landline to eSIM everything was sorted once porting was completed, little glitch in dashboard with temporary number now resolved

I have been with ONSIM for a number of years now, using landline Sims and desk phone twinning, the service is great with access to EE network and O2.

The level of customer service you receive from these guys is unreal, support is primarily via email with the most serious being sorted first.

What's more important to mention is although this is a SMB their support agents aren't reading off diagnostic queues or scripts - they actually know what they are talking about.

Very pleased and highly recommended

Quick clear response, asking a couple of very specific technical questions Chris at Onsim responded quickly and clearly. Great service

I have been using OnSIM for the past two years, and without hesitation, I can say this is one of the best services I have ever experienced. Chris and Pete have been absolutely exceptional throughout — professional, responsive, and genuinely committed to delivering a high-quality service.

From the outset, the setup process was smooth and straightforward. They took the time to understand exactly what I needed and ensured everything was configured correctly from day one. The landline SIM solution itself has been flawless — reliable, consistent, and perfectly suited to my business operations. I’ve had no downtime issues, and the call quality has always been excellent.

What truly sets OnSIM apart, however, is the level of customer support. Chris and Pete are incredibly responsive — messages are answered quickly, often within a few minutes, and always with clear, practical solutions. You never feel like just another customer; they give a very personal, hands-on service which is rare to find these days.

Even when I’ve had queries outside of standard expectations, they’ve gone above and beyond to help. Their technical knowledge is impressive, and they explain things in a way that’s easy to understand, without any jargon. It’s clear they take pride in what they do and genuinely care about their clients.

Another big plus is their proactive approach. They don’t just react to issues — they anticipate potential problems and offer solutions before they become a concern. That level of attention to detail gives real peace of mind, especially when running a business where communication is critical.

Over the past two years, the consistency of their service has been outstanding. There’s never been a dip in quality, and that reliability is something I really value. It allows me to focus on my business without worrying about phone systems or connectivity.

In a market where many providers overpromise and underdeliver, OnSIM — particularly Chris and Pete — truly stands out. They combine excellent technology with even better customer service, which is a rare combination.

I would highly recommend OnSIM to anyone looking for a dependable, professional, and customer-focused landline SIM provider. You won’t be disappointed.

The fact that they port my landline number to a sim card service, and worked very well, onsim support at hand at every stage of the process. Up and running in no time, friendly and helpful support, also the onsim dashboard is great, shows alot of useful info about your account and usage. Would recommend to anyone. Cheers Onsim.

I’ve recently started using OnSim.uk for my business phone setup and have been really impressed with both the service and the support team so far. From the first enquiry through to getting my greeting, voicemail and call routing working exactly how I needed, every support interaction has been quick, patient and very clear.I run a domestic appliance service and we also run a busy pub, and I’m now in the process of moving a few businesses over to OnSim because the flexibility suits how we work. They’ve helped me set up a proper business greeting, UK ring tone, voicemail and a temporary landline number while we get our main number ready to port, and they stuck with it until everything was working perfectly. One thing I’ve really appreciated is learning about some of the more advanced features, like being able to dial *21 followed by a phone number to divert calls while you’re calling that’s something I didn’t even know was possible before and it’s genuinely useful for a small business that’s often on the move. I’m sure there are more features like this hidden away that I’ll discover as I go, which brings me to my only real suggestion.The only area I’d like to see improved is the website and documentation. The platform is powerful, but it would be great if the site had either a bit more information on what’s possible, or if that information is already there, for it to be a little easier to find and navigate. For new users, clearer examples and a more obvious “features and how to” section would make it much easier to get the most out of what OnSim can do without having to contact support every time.Overall, I’m very happy with OnSim and the level of service I’ve received, and I’m confident enough in them that I’m moving multiple business numbers across. If you’re a small business looking for a flexible, UK-based telephony solution with real people at the other end of support, I’d definitely recommend giving OnSim a try.

Signing up to Onsim was very straight forward, with their support team making the migration from my existing supplier a very easy process. Their customer support team were also very quick to reply to follow up queries with useful links and advice. Would recommend! 5*

I found it relatively easy to set up. The support team are quite responsive and the fact they also sell desktop phones to complement the software shows good all round thinking.

I ported in my landline number so I could escape an ISP wanting to provide a landline badly. The call quality on VoLTE & WiFi calling is incredible.
When I had some audio quality issues, I found support very helpful. It was ultimately my iPhone handset at fault, but the problem was taken seriously and investigated thoroughly.

I've just started helping an old friend who wanted to retain his landline number with a mobile phone given the "analogue switch-off" and endless problems with his dreadful quality old long copper line.

Onsim have an innovative service, and so far the online booking service and the support staff have been great. The new esim has been easily set-up and is working well. Very little of the usual GDPR nonsense (just the essentials) and excuses because "You're not the applicant so we cannot talk with you" . Well done ONsim support.

Obviously the acid test is coming up next. The porting forms have been accepted and processed, so I now await with anticipation whether ONsim can deliver the same excellence and the landline number is easily and flawlessly ported to the mobile phone. Hopefully I'll write a follow up review in a couple of weeks.

OnSim has quietly done what most telecom providers overcomplicate. Their eSIM gives me a landline number and a mobile line on the same handset, integrates cleanly with SIP, and delivers hunt groups and the full suite of cloud telephony features without forcing me into clunky hardware or separate devices. It behaves like a proper business phone system, yet lives seamlessly inside my mobile. Setup was intuitive, the configuration was logical, and the overall architecture feels designed by people who actually understand how modern businesses operate rather than how legacy carriers bill.

What truly sets OnSim apart is the support. Response times were sharp, communication was clear, and every question was handled thoroughly without hand-offs or scripted replies. Porting numbers from BT Cloud, despite the painfully bureaucratic form required at my end, was executed smoothly and without drama. That alone deserves recognition. In a market crowded with providers who promise simplicity and deliver friction, OnSim delivered exactly what was needed, precisely when it was needed.

Exemplary service - helpful, prompt and professional.

Paid Onsim since mid 2025 and have not received service from them since inspite of numerous telephone calls and emails. Appalling customer service. If you are contemplating using this e sim I would strongly advise you chose another service provider.

Great company with great service. Easy to set up and bridges the gap of having a landline but having the flexibility of a mobile phone and also not being tied down by a big contract. Important in business! Willing to work with you with any request big or small.

Very affordable and since joining they’ve updated their online dashboard to give great analytics which help with making business decisions and getting consumer insights. I can see them improving monthly so wouldn’t be surprised if more features are added in the future.

Customer service has always been perfect. Prompt emails answering any questions I had and voice calls with people who care (not outsourced call centres so very easy to understand and prompt in help)

When you sign up you get a SIM card or eSIM de listed. (You get a choice) and support along the way. Direct debit with transparent information, call logs and answer phone functions as standard.

I did have connection problems occasionally but these were resolved at the beginning and it has been smooth sailing since.

Will consider onsim when expanding my business in the future.

I have had a brilliant experience with Onsim.

Their system is reliable and user-friendly, with excellent multi-device support – we currently use it across desk phones and desktop applications, which keeps our team connected and efficient. Features like voicemail-to-email, call forwarding, and live call logs make day-to-day operations much easier to manage.

A special mention to Chris and Pete, who have both been fantastic throughout. Their customer service is exceptional – always quick to respond, helpful, and genuinely committed to finding solutions. It’s refreshing to deal with a team that actually listens and supports you every step of the way.

We’ve also noticed that Onsim is constantly evolving, with regular improvements and updates based on user feedback – something we really appreciate as a growing business.

Highly recommend Onsim to any company looking for a reliable telecoms provider backed by real people who care.
User m23568

Hands down the best customer service I've ever had from a mobile operator. Nothing was too much trouble and the advisors I spoke to were extremely knowledgeable and friendly. We've now got a fully functioning 'landline' number that we can take anywhere. Staying in touch with your customers is priceless. So glad we picked ONSIM for our provider!

Great Service superb help and assistance within less than 10 mins my problems where sorted and I was able to access everything I needed can't recommend them highly enough

I am not remotely "techie" and needed my hand holding from the start of the process (even to needing to ask advice on appropriate mobile 'phones). Chris has been outstanding, helpful and immensely patient and now I have a fully functional new (and very flexible) 'phone system. What a contrast from the service provider I left. All success to Onsim, and thanks again.

Worse company ever a phone company with no phone on any of their emails messages to raise concerns beware .very slow response to a 3 month problem not recommended at all..

My concern listed here . After 3 months ..

You are actually taking liberties now no to to use sim slot to use so eventually sent me QR code a week ago. But say you sent one in December but you didn't
QR code added to my phone but this number still not connecting as have tried to ring the number issued on my account. Now you block my account and block my messages after they demand 3 months of rental for nothing received from your poor service you threaten further action.
So have you 12 pound if you are so desperate for money but provide an actual service first . Very poor customer service.
I recommend Would set yourself in good practice or your customer base will dwindle with bad reviews.

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