Was leaving EE and got my code but decided to stay and now have a new phone with a new number. My code has expired. Can I manage to keep my old number?
I assume that what you're saying is, you requested your PAC from EE, but didn't use it and have separately bought a new phone with a new number.
If that is the case, then yes your PAC will expire after 30days, and your existing phone/line/number will continue as if nothing has happened. It's the use of the PAC that serves as contract termination, not requesting it.
