Your post is a bit confusing. You're saying "activation lock" but what you're describing sounds more like a carrier (or subsidy) lock.
If your phone has been activation locked, that means that someone has connected it to their Apple Account. The only way to remove the activation lock is with the Apple Account creditials. TMobile can't do anything.
If you're trying to get the carrier lock removed so that you can use the phone on a different carrier, yes, you need to speak to the carrier. Did TMobile tell you they have put in the request? Or that the request is completed? If the former, call them back and ask them how long they expect it to take. Generally, you get an email or something letting you know it's complete. If TMobile told you that it's complete, you may need to restore the phone.
Restore your iPhone, iPad, or iPod to factory settings using a computer - Apple Support