phone replacement

Did you buy either AppleCare+ or insurance from T-Mobile?

If the former, take it to Apple. If the latter, take it to T-Mobile. If neither, make an appointment at the Genius Bar of your local Apple Store and pay for an out of warranty replacement display, or out of warranty replacement phone, or buy a new one depending on how badly it's damaged.

As long as it's in the same country where the iPhone was designated for retail sale, Apple should be able to replace pretty much any version of any iPhone model currently supported for "repair" at an Apple Store or via mail-in service. If it's a T-Mobile phone then the replacement will be an identical T-Mobile phone other than the model number has a slight modification (starting with an N). However, they may not have your model of replacement device in stock and may need to send out a replacement from a warehouse. A replacement could be sent to an Apple Store or shipped directly to you. I believe for the mail-in service they'll send out a box.

iPhone Repair - Official Apple Support

Whether you can get it replaced, for how much, and by whom, will depend on what model phone you have, where you got it, and why it is "no longer working".