> While I had a PIN associated with my SIM, I still do not know how the thief was able to get past this the first time, I changed this PIN on the call.
If he's really talking about the SIM PIN, I don't think having one helps against this kind of attack. The SIM PIN is to prevent people in possession of your physical SIM from using your cellular account for voice or data.
What you need with T-Mobile is a separate PIN that is required for porting out your number [1]. You set this PIN up by calling support.
I thought of the port out pin too, but I think the attacker convinced t-mobile support to activate a different SIM. I don't think the PIN does anything in that scenario.
If he's really talking about the SIM PIN, I don't think having one helps against this kind of attack. The SIM PIN is to prevent people in possession of your physical SIM from using your cellular account for voice or data.
What you need with T-Mobile is a separate PIN that is required for porting out your number [1]. You set this PIN up by calling support.
[1] https://www.t-mobile.com/customers/secure