I can get an official unlock code from the carrier. All the unofficial unlocks seem to require a SIM from a different carrier to complete the unlock process. I do not have a second SIM now. I intend to use the phone when traveling internationally and won't have the second SIM until then.
With an official unlock code from the T-Mobile, will I still need the 2nd SIM to complete the process? I'd like to get this done ahead of time.