Iphone SE (2022) Unlock sim - fully paid - no longer with t-mobile

I possess an iPhone SE (2022) which was originally acquired through T-Mobile's Equipment Installment Plan. The device is fully paid off, and I have since switched to a different carrier. However, I've encountered an issue where the phone is not accepting the new SIM card, indicating that it is still locked to T-Mobile. Could you assist me in unlocking the SIM so that I can use it with my current service provider?