You need to be a customer of Tmobile USA and meet the requirements in the link below
https://www.t-mobile.com/responsibility/consumer-info/policies/sim-unlock-policy
I am a user of Tmobile USA. The device has been activated on my Tmobile for more than 3 years. Meet the requirements in the link.
I am a user of Tmobile USA. The device has been activated on my Tmobile for more than 3 years. Meet the requirements in the link.
Then you need to call T-Mobile at 611 from your T-Mobile line, verify your account. And request the SIM unlock. iPhone SIM unlocks can take weeks because T-Mobile sends the request to Apple and it is up to Apple to complete. You can also reach T-Mobile on Facebook or Twitter, verify your account, and request the SIM unlock that way. T-Mobile can only SIM unlock devices SIM locked to T-Mobile.