Switching from O2 to Three? It's a straightforward process to keep your existing phone number.

Step 1: Get a PAC Code from O2

If you’d like to move your phone number from O2 to Three, the first step is getting your Porting Authorisation Code (or PAC Code) from O2.

There are three ways to get a PAC Code from O2:

  1. Online: You can get a PAC Code from O2 by logging in to the My O2 website. Once you've logged in, go to My details > Thinking of switching from O2?.
  2. By Text Message: You can get an O2 PAC Code sent to you via SMS text message. Text PAC to 65075 to receive a PAC Code from O2.
  3. By Phone: You can get a PAC Code by calling O2. To do this, call them on:
    • For O2 Pay Monthly, dial 202 (or 0344 8090202 from any other phone)
    • For O2 Pay As You Go, dial 4445 (or 0344 8090222 from any other phone)
    You'll need to call during O2's opening hours (Monday-Friday 8am-9pm, Saturday 8am-8pm, Sunday 8am-6pm).

Here are some key things to know:

  • The PAC Code from O2 should consist of six numbers with TEL at the start (e.g. TEL 123 456).
  • Your PAC Code is valid for 30 days. If you don't use it during this time, the PAC Code will expire and you'll need to request a new one.
  • You shouldn't close your account at O2: it'll be closed automatically when your phone number is transferred to Three.

Still in contract with O2? If so, you may need to pay an early exit fee on your bill from O2. To find out how much this would be, text INFO to 85075.

Don’t want to keep your O2 phone number? You can switch to Three without taking your phone number with you. If you'd like to do this, get a STAC Code from O2 instead.

O2 STAC Code (Leave O2 Without Keeping Your Number)

If you’d like to leave O2 without keeping your phone number, you’ll need to request a STAC Code rather than a PAC Code. There are three ways to get a STAC Code from O2:

  1. Online: You can get a STAC Code from O2 by logging in to the My O2 website. After logging in, go to My details > Thinking of switching from O2?.
  2. By Text Message: You can get an O2 STAC Code sent to you via SMS text message. Text STAC to 75075 to receive a STAC Code from O2.
  3. By Phone: You can get a STAC Code by calling O2. Call them on:
    • For O2 Pay Monthly, dial 202 (or 0344 8090202 from any other phone)
    • For O2 Pay As You Go, dial 4445 (or 0344 8090222 from any other phone)
    You'll need to call during O2's opening hours (Monday-Friday 8am-9pm, Saturday 8am-8pm, Sunday 8am-6pm).

Once you’ve gotten your STAC Code from O2, the rest of the process for joining Three remains the same.

Step 2: Order your new phone or SIM card from Three's website

You should now order your new phone or SIM card using the Three website. Please select the type of tariff you're intending to move to:

If you're looking for a SIM card from Three, the following deals from £5/month are currently most popular:

Network Data Monthly Cost
Three
  • Unlimited mins
  • Unlimited texts
3GB
data
£5.00
per month
24 month contract
Monthly cost will rise each April by £1
See deal  
Three
  • Unlimited mins
  • Unlimited texts
12GB
data
£6.00
per month
12 month contract
Monthly cost will rise each April by £1.25
See deal  
Three
  • Unlimited mins
  • Unlimited texts
30GB
data
£7.00
per month
12 month contract
Monthly cost will rise each April by £1.25
See deal  
Three
  • Unlimited mins
  • Unlimited texts
120GB
data
£10.00
per month
12 month contract
Monthly cost will rise each April by £1.50
See deal  
Three
  • Unlimited mins
  • Unlimited texts
Unlimited
data
£20.00
per month
24 month contract
Monthly cost will rise each April by £1.50
See deal  

For a full list of available tariffs and the latest Three deals, please refer to this page on Three's website.

Alternatively, if you're getting your Three plan from a reseller, tap on their logo for more information:

Three will assign you with a temporary phone number during the transition process. This will allow you to test out the service before you finally transfer your phone number to Three.

Step 3: Give the PAC Code to Three

Once your new phone or SIM card arrives from Three, switch it on and make sure everything's working properly. If, for whatever reason, you need to return or change the handset or SIM card, it's best to do this before transferring your phone number.

Once you're happy to continue with the phone number transfer, contact Three and provide them with your PAC Code from O2.

Your PAC Code should be entered on Three's online form. Alternatively, you can give the PAC Code to Three by calling 333 on your Three handset. You can also call 0333 338 1001 from any other phone.

If you have a STAC Code from O2 rather than a PAC Code, this can be provided to Three in the exact same way.

Providing your PAC Code to Three
The PAC Code should be submitted through a form on Three's website.

Remember:

  • You must provide the PAC Code to Three within 30 days of it being issued by O2. If the PAC Code has already expired, you'll need to return to step 1 and request a new PAC Code from O2.
  • O2 Pay As You Go customers: Try to use up your remaining credit as it can't be transferred to Three.

Step 4: Phone Number Transferred (Next Working Day)

As long as you've submitted your PAC Code to Three before 5pm, your phone number transfer will normally be scheduled for the next working day (Monday to Friday only, excluding English bank holidays). After 5pm, you'll need to wait one extra working day for your number to be transferred.

On the day of the transfer, you'll momentarily lose coverage on both mobile networks. When this happens, restart your handset on Three. You should find that the Three phone or SIM card will now associated with your original phone number.

  • If you see an error message (e.g. "SIM card registration failed"), this means it's time to restart your phone.
  • Once the phone number has been transferred to Three, your account on O2 will automatically be closed. You'll receive a final bill from O2 for any outstanding charges.

Get the Latest Deals from Three →

Any Other Questions?

In case of any problems during the transfer of your phone number, you should contact your new mobile network (Three) with details of the problem.

If you have any other questions on using a PAC Code, please see my in-depth guide to transferring your phone number between networks. You can also read the comments below from other visitors to this website.

← Full Article: "PAC Codes - How to transfer your mobile number when switching networks"

Your Comments 1,966 so far

We'd love to hear your comments on transferring a phone number from O2 to Three. The comments below are from people who've made the same transfer. You can add your own comments here.

To view all 1966 comments about transferring a phone number, please visit the main PAC Code article.

    • Ken replied:

      Hi Niamh,
      Thanks for your comment. Have you followed the entire process as discussed above in this article (getting a PAC Code from O2 and giving it to Three)? Once you’ve done this, your O2 phone number will be moved to Three (before this, your Three SIM card will be assigned a temporary phone number).
      Ken

  • Rhonda said:

    Hi.

    I think I made a stupid mistake. I transferred my number to a SIM-Only deal from O2 to Three but I did so without activating my SIM first. I had a phone on contract with O2 but the contract has ended so the phone is mine now. I’m not sure if I need to get it unlocked first before using my Three SIM. I don’t have any network coverage on my O2 SIM and I’m unable to activate my Three SIM. Help!

    thanks,
    rhonda

    • Ken replied:

      Hi Rhonda,
      Thanks for your comment. It may be necessary to unlock your handset from O2 before you’re able to use it on Three. I believe that O2 will typically lock iPhones on their network – are you using an iPhone or is it a different device? There’s more information about how to unlock your handset here (you may also find it interesting to read the guide on unlocking an iPhone and unlocking a Samsung Galaxy). It should be free to unlock your handset from O2 as you’re a Pay Monthly customer.
      Hope this helps,
      Ken

  • David said:

    What about any credit on the SIM you are transferring to? I have a 3 PAYG SIM with some credit, and want to transfer the number from a O2 PAYG SIM. Once the number is transferred to 3, will I still have the credit from the previous 3 number?

    Also, what happens to the previous 3 number?

    • Ken replied:

      Hi David,
      The SIM card on which you’re transferring your phone number to will retain any credit it had before the incoming transfer. So any credit currently on your Three SIM card will still be there after the transfer is complete.
      Hope this helps!
      Ken

  • Ken said:

    Having switched from O2 to 3 without problems I have noticed that my phone (a moto G) shows its phone number as being the original number assigned to the 3 SIM rather than the phone number I ported from O2.

    Is there anyway to ensure that the correct number is displayed for my phone?

    • Ken replied:

      Hi Ken,

      Thanks for your comment. Is this a problem with your Caller ID (the number which shows when you make a phone call) or a problem on the handset itself? For caller ID, the best thing to do is to contact Three Customer Services (call 333 from your Three handset). For the latter (a problem on your handset), a quick restart will normally solve the problem (you may also need to re-register through apps such as WhatsApp).

      Hope this helps!

      Ken

      • Ken replied:

        Hi Ken,

        Thanks for the reply. I was able to edit the SIM number on another Phone (Samsung Galaxy ACE DUOS) by going to Contacts/Settings/Own Numbers and editing My Number.

        So it now shows up correctly on both the phone and caller ID.

  • J Frank said:

    I have two contract one with o2 and other with three, I would like to swap the number. Is this possible or do i need to stop the contract. I want both the contracts rolling.
    one (three) contracts started in dec 2012 and other (o2) ends in Dec 2013, Please help.
    Many thanks in Advance

  • Alex said:

    Hi,
    I am transferring from o2 pay as you go to 3pay monthly, I have had my pac code and given this to 3. I was told the transfer would be done on Tuesday, so I checked my old phone and there was no signal, later my partner called my old number to check that it had been transferred and someone else answered my number! The number has been transferred to another 3 sim! I have then called 3 and asked them for my transfer straight away, but they have told me that they have to get more information for o2 and I have to wait another 72 hours! Am I within my rights to speak to their supervisor and get this done today??? Any help would be much appreciated 🙂

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