Phone number

[Na1]

If I switch my Giffgaff phone number over to my new Three phone, will it override any other phone numbers linked to that phone?

[PeteG]

Hello there.

It's unclear what you mean by other phone numbers linked to that phone, are you referring to other SIM cards you use on the phone? 

Pete. 

[jr0]

Hi Na1

when you moving/changing/switching providers (eg Giffgaff -> Three) you can ask to keep your phone number (sometimes aka porting or portability).

visit: https://www.uswitch.com/mobiles/guides/porting-your-mobile-phone-number/