Hi, I need help unlocking my iPhone 12 Pro Max.

If your T-Mobile account and device meet all of the SIM Unlock Policy requirements that you can find here:.  SIM Unlock Policy | Unlock Your Mobile Wireless Device | T-Mobile

Reach out to Customer Care to verify you have met all of the requirements and to have the SIM unlock requested.  SIM unlocks for iPhones can take up to 3 weeks and longer.  T-Mobile submits the SIM unlock request to Apple and it is then up to Apple to complete.