BT One Phone has shut down: what happened, and your options now
BT One Phone was switched off in March 2026 with no press release. Where its customers went, the costs nobody mentioned, and what you can still do about it.
BT One Phone Has Been Switched Off - Your Options Now
BT One Phone was decommissioned in March 2026. If you were rushed onto BT Cloud Voice and it is not working out, or you took a stopgap and still need a proper home for your numbers, here is what to do next.
Why BT One Phone Is Being Withdrawn
BT haven't specifically said why they are withdrawing their One Phone service but our best guess is that it's too expensive for them to maintain and support. BT’s move reflects the industry-wide shift away from old analogue and legacy systems and consolidation toward digital voice services - voice over internet protocol (VoIP) delivered over broadband and apps. It's worth noting that these VoIP services are super high profit margin for providers but are known to be a lot less reliable than the services that they are set to replace with many customers expressing frustration and downtime during and after the switch.
Why This Matters to Your Business
BT One Phone was switched off in March 2026, and its customers were pushed in different directions - most commonly onto BT Cloud Voice on new multi-year contracts, some to Teams Phone, some to stopgap providers.
The catch nobody explained:
- - Cloud Voice is an app-and-internet phone system, not the SIM-based, network-level service One Phone was - it works differently in the van, on site and in weak Wi-Fi.
- - Features One Phone included (recording, hunt groups, auto attendant) became per-user or per-site paid add-ons.
- - None of it is permanent. Your numbers can be ported to a provider you actually chose, at any time.
ONSIM works the way One Phone worked - your numbers on SIMs, at network level, no apps - which is why ex-One Phone businesses land here. Read our full write-up of what happened to BT One Phone.
Replace BT One Phone with ONSIM
BT One Phone was withdrawn in March 2026, and its customers were scattered across Cloud Voice, Teams Phone and stopgaps. ONSIM is the alternative that works the way BT One Phone did - on a SIM, at network level - and lets you keep your UK landline (and mobile) numbers wherever they ended up. Moving is not locked to a deadline: numbers port out of Cloud Voice or any interim provider at any time.
A Direct BT One Phone Alternative
ONSIM replaces BT One Phone giving you access to the same type of service, features and we even use EE's masts so coverage will be identical.
Fast, Managed Migration
We handle the switch from BT One Phone end to end. For compatible devices, we can also provide a SIM or eSIM so the transition is quick and seamless.
No Apps. No VoIP Instability.
Unlike app-based VoIP services, ONSIM operates at network level - via SIM/eSIM connected to EE's mobile network. That means consistent call quality, no app logins, and no dropped calls.
Keep Your Number, Long-term
Your business numbers are yours. You can port them to ONSIM today and, if needed, move them again later. ONSIM will never prevent you porting out your number to another provider.
7,500+
Customers
BT One Phone vs ONSIM
A simple side-by-side comparison for ex BT One Phone businesses choosing their permanent home.
| Feature | BT One Phone | ONSIM Virtual Landline |
|---|---|---|
| Service status | Switched off (March 2026) | Available now |
| Real UK landline number (01 / 02 / 03) | Yes | Yes |
| Answer calls on mobile | Limited | Yes |
| Make call displaying landline number | Yes | Yes |
| Underlying mobile network | EE | EE |
| Native Call Recording | Yes | Yes - more advanced |
| Hunt Groups | Yes | Yes |
| Conference bridges | Yes | Yes |
| PBX or desk phone required | Often | No (but can be used) |
| Apps required | Varies | No (network-level) |
| Call reliability | Variable | Consistent |
| Number porting | Yes | Yes (managed) |
| Single Contract and Bill | Yes | Yes |
BT One Phone was withdrawn in March 2026. Wherever your numbers went in the scramble, they can be ported to ONSIM at any time - check yours with the free porting checker at /tools/porting-checker/.
FAQs
Frequently Asked Questions
Seamlessly migrating your services from BT One Phone to ONSIM.
How does ONSIM compare to BT One Phone?
ONSIM is the closest replacement possible to BT's One Phone service. We match nearly every feature including Native mobile dialling (no apps), custom forwarding, hunt-groups, landline caller IDs, call recording, reporting and more. We even use EE's masts so the coverage will be identical.
Are there any features ONSIM doesn't provide that we got with BT One Phone?
Yes. ONSIM do not provide a native management app (the BT One Phone App) - you can still make changes to your settings in real time but this is managed through a secure web portal. We also do not provide a managed directory service which was also included in this app.
Are there any features ONSIM provide that BT One Phone did not?
Yes, loads. - inclusive roaming in 39 countries (including USA), cheap international calls, Queues, Conference Bridges, API access, Black/White Lists, Full TOD routing, roaming controls, international numbers and multi-country support, SMS Gateway, Call Parking and much more.
Is ONSIM a cloud-based calling (VoIP) app?
NO! ONSIM is a mobile service just like BT One Phone - it doesn't use Apps or VoIP to make or receive calls but just like One Phone you can add IP phones and Apps if you wanted to.
Can I keep my existing numbers?
Yes. You can port your existing landline and mobile numbers to ONSIM from BT One Phone.
Can I make outbound calls showing my landline number?
Yes. You can display landline or mobile numbers when you call out - multiple users can even share the same number to dial out
Is call quality reliable?
Yes. Just like BT One Phone calls are routed over mobile networks and VoLTE not VoIP
How quickly can I get started?
We can set up your service instantly. Porting mobile numbers takes 24 hours and porting landline numbers takes 5-10 working days (this is the time taken to process the request by BT not downtime - your numbers will remain active during this period)
What does it cost?
We offer unlimited calls and texts for £10/user/month - various data packages can be added - full pricing is listed here. If you have a team of more than 50 users please reach out to sales@onsim.uk for a custom quote.
I was moved to BT Cloud Voice when One Phone closed - can I still switch?
Yes. UK number portability is mandatory, so your landline and mobile numbers can be ported from Cloud Voice (or any interim provider) to ONSIM at any time. If you signed a new Cloud Voice contract during the migration, check its terms for early exit charges before you commit - and note that during the shutdown some customers reported being quoted early termination fees on old BT One Phone contracts too, with waivers hard to get in writing. We are happy to time your port around your contract dates.
Will switching disrupt my current phone numbers?
No. We have a great deal (15 years) of experience porting numbers from BT and as a reputable provider we help manage the porting process for our customers every step of the way. This allows us to transfer your numbers with minimal disruption.
Switch from BT One Phone to ONSIM today
Join the thousands of customers that already use ONSIM making the switch from BT One Phone as seamless as possible without apps or VoIP!
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