Yes, you can keep your number when moving to another network. To do this, request a PAC and give it to your new provider. They’ll transfer your number to your new account and your old Three account will close.
To get your PAC, text PAC and your date of birth to 65075 – your text should look like this:
We’ll send your PAC by text and it’ll be available for 30 days. If you don’t use it within 30 days, your contract with us will carry on as normal.