Switch from O2 to Three and keep your number using a PAC code

Last Updated: 29th July 2025

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Are you thinking about leaving O2 and switching to Three? Then you're in the right place! Switching networks and keeping your number in 2025 is simple and easy thanks to Ofcom's policy changes.

We've put together a quick and easy to use switching guide. Our guides allow you to select the network you wish to switch to and from, and you will be given a step by step guide on how to keep your number and move to a new SIM Only Deal.

It is worth noting that if you wish to join Three and get a new number then you can use a STAC code in order to get a new number and will cancel your existing contract.

Joining Three and leaving O2

Quick Network Switching Tool
Select which network you would like to switch from and to and we will give you precise instructions on how to keep your number when switching to a new SIM Only Deal.

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Joining Three and transferring your number from O2 is a simple process and usually takes no longer than 1-2 working days.

The process which will go through in more detail below involves requesting a PAC code from O2 and handing it to Three.

You can either hand the PAC code over to Three during the ordering process or after you have received your new SIM card or eSIM has been activated.

1. Request a PAC code from O2

Switching from O2 and keeping your current phone number is easy. There is no need to commit a new number to memory or update all your contacts!

Here is how to get your PAC (Porting Authorisation Code) from O2:

Text: From your O2 phone, text "PAC" to 65075. You will receive a text back with your code within 60 seconds. This is a free service from Ofcom (the UK's communications regulator).
Online: Log in to your O2 account online ("My O2") and request your PAC code.
Phone: Call O2 customer service on 202 from your O2 phone or 0344 809 0202 from another phone.
- Their customer support is open;
  - Monday - Friday: 8am - 9pm
  - Saturday: 8am - 8pm
  - Sunday: 8am - 6pm
In-store: Pop into your nearest O2 store and request to leave.

Your PAC code is valid for 30 days, so you can request it before you get your new SIM card. You can retrieve it from your O2 account or by calling O2 if you lose it.

If you want a new number and do not wish to keep your current number, you will need to request an STAC code instead of a PAC code. Text "STAC" to 75075 to get your STAC code.

2. Order a SIM only deal from Three

If you haven't yet ordered your new Three SIM Only deal, you can use our free comparison engine, which will show you the cheapest Three deals available on the market.

Compare Three SIM Only Deals

If you already have your new SIM Card, feel free to skip to step 3 of this article

During the ordering process you may be given the opportunity to share your PAC code from O2 to Three, if you choose this option then the number transfer process will start once your new sim card arrives and you activate it in by putting it in your phone and turning it on, this also means you can skip to step 4 of this article if you wish!

If you are not given the opportunity to hand over your PAC code when ordering then there's no need to panic. Once your new sim card from Three has arrived, just continue to step 3 of this article.

It is also worth calling out that it doesn't matter if you are able to hand over your PAC code from O2 whilst buying your new sim from Three or not it's just slightly more convenient but the outcome is the same!

3. Give the PAC code to Three

Giving Three your PAC code is super simple:

Online: Just complete a quick form on the Three website and enter your PAC code. Done!
Over the phone: Call Three on 333 from your Three SIM or 0333 338 1001 from any other phone.
- Their customer service line is open;
  - Monday through Friday, 8 am to 8 pm
  - Saturday and Sunday, 9 am to 6 pm.
In-store: Pop into your nearest Three-store location, and a friendly advisor will help you switch your number.

Relax and wait: Within 1-2 working days, your phone number will be transferred to Three. Easy peasy!

Remember: Your PAC code is valid for 30 days, so give it to Three within that time.