I’m still using a 5c, so am eager to upgrade after next week's announcement. My AT&T contract ends 9/22, and I’d like to try T-Mobile. I have grandfathered “unlimiited data” with AT&T, so I’d rather not cancel that account unless I’m sure I'm happy with T-Mobile's coverage. I guess the best way is to buy a new unlocked phone with a T-Mobile SIM, while holding on to old phone with active AT&T account. Use T-Mobile's free 200 MB of monthly data to test new phone for a month in different locales (using my old phone for hardcore data tasks), then either choose T-Mobile, port over old number, cancel AT&T, sell old phone........or else choose AT&T, insert an AT&T SIM into new phone, cancel T-Mobile, and sell old phone. Make sense? Am I forgetting anything?