How do I remove a carrier lock?

We can't do that. They won't help if the caller cannot provide account details. Only you can do this.

Here's a link to the main U.S. page.

Click the chat button towards the lower right.

Sorry, but ONLY T-Mobile can release the Carrier Lock on your device.

See:

How to unlock your iPhone for use with a different carrier - Apple Support

We understand you situation, but we have no control over this.

Only T-Mobile can unlock the phone. There are no other options.

We will not be able to help you. T-Mobile will only speak directly to their customers. They will not speak to us.

There is nothing more that we can do to help.

Then you are faced w/ a dilemma.