How to Switch from BT Mobile to Three
If you are considering moving from BT Mobile to Three, you are likely weighing up Three's wider 5G coverage and different data options. This guide covers what to check, how to switch, and what to watch out for when making the move.
Before you switch
First, check your BT Mobile contract end date. If you are still within your minimum term, BT Mobile will charge an early termination fee based on your remaining contract value, minus savings and discounts. You can find the exact amount by contacting BT Mobile customer service.
Be aware that leaving BT Mobile may mean losing access to any BT-linked email addresses or bundled services, such as BT Wi-Fi or BT Sport. Make sure to back up any important data and update your contact details with any services that use your BT Mobile email address.
How to switch, step by step
- Check your contract status with BT Mobile. Log in to your BT account or call customer service to confirm your contract end date and any exit fees.
- Request a PAC or STAC code. To keep your number, text PAC to 65075 from your BT Mobile phone. If you want a new number, text STAC to 75075. Both codes are valid for 30 days.
- Sign up with Three. During sign-up, provide your PAC or STAC code. Three will handle the number transfer. If you submit your PAC before 3pm on a weekday, your number will usually transfer within one working day.
- Insert your new Three SIM card. Once your number has transferred, your BT Mobile service will automatically end. If you are switching broadband as well, check if an engineer visit is needed. For Openreach-based broadband, the process is usually automatic, but switching to a different network type may require a cease-and-reprovide process.
- For energy services, simply sign up with your new supplier. The new supplier will manage the switch, which typically takes five working days under the Energy Switch Guarantee.
What to watch out for
- Early termination charges: Leaving BT Mobile before your contract ends can result in significant fees. Always check your contract and calculate potential charges before switching.
- Number transfer delays: Delays can occur if you provide your PAC code late in the day or if there are issues with your account details. Submit your PAC as early as possible to avoid disruption.
- Device compatibility: Ensure your handset is unlocked and compatible with Three's network frequencies before switching. Contact Three if you are unsure.
Comparison of BT Mobile and Three UK Mobile Services (2026)
| Feature | BT Mobile | Three UK |
|---|---|---|
| 5G Coverage | Approximately 89% of UK population | Approximately 62% of UK population |
| Data Allowance Options | 6GB, 15GB, 30GB, 100GB | 15GB, 30GB, 60GB, Unlimited |
| Monthly Plan Pricing | 6GB: £62.74, 15GB: £67.80, 30GB: £73.88, 100GB: £84.01 | 15GB: £7.00, 30GB: £8.00, 60GB: £9.00, Unlimited: £24.00 |
Sources: BT Mobile and Three UK official websites, 2026.
Switch with Lodo
Want to make switching from BT Mobile to Three as easy as possible? Lodo is the simplest way to do it.
With Lodo, we will sign you up with Three, request your PAC code, port your number, and cancel your BT Mobile plan. If anything goes wrong, we resolve it with the providers directly. Free, no catch. Switch with Lodo for free
Frequently asked questions
How much does it cost to leave BT Mobile?
If you cancel your BT Mobile service before the end of your minimum contract period, you'll incur an early termination fee. This fee is calculated based on the remaining months of your contract, minus any costs BT saves from your early departure. For example, if you have four months left at £35 per month, the fee would be £67.32. (bt.com)
How long does the switch take?
Transferring your mobile number to Three typically takes one working day if you submit your request before 5pm on a weekday. If submitted later, the transfer will occur on the next working day. (three.co.uk)
Will I lose my phone number?
No, you can keep your existing phone number when switching to Three by obtaining a Porting Authorisation Code (PAC) from BT Mobile and providing it to Three. (three.co.uk)
Can I switch if I am still in contract?
Yes, you can switch to Three while still under contract with BT Mobile. However, you may incur an early termination fee for ending your contract early. (bt.com)
Do I need to contact BT Mobile or does Three handle it?
When switching to Three, you need to contact BT Mobile to obtain a PAC or STAC code. Three will then handle the transfer process. (three.co.uk)
What happens if something goes wrong during the switch?
If there are issues during the switching process, such as delays or incorrect information, you may be entitled to compensation. It's advisable to contact BT Mobile or Three customer service for assistance. (bt.com)
Is there any downtime?
There may be a brief period of downtime during the number transfer process, but it is typically minimal. To ensure a smooth transition, keep your old account active until the transfer is complete. (three.co.uk)
Anything else specific to this provider pair?
When switching from BT Mobile to Three, ensure you have a compatible device and that Three's network coverage meets your needs. Additionally, be aware of any outstanding charges or obligations with BT Mobile before initiating the switch. (bt.com)