Last month, after 12-15 years with Sprint, I left to go to T-Mobile on a pre-pay plan. An important aspect of porting my cell number over was to provide my account number from Sprint. I had always been on-contract over the years, renewing/upgrading every 2 -3 years. Now that I'm with T-Mobile, no where in my pre-paid information sheet (which they provided upon sign up) is an account number. Would I need a T-Mobile account number if ever down the line I want to switch over to ATT and port my number? Thanks!