This device is not recognized or common.
You have two options:
First disassemble the device and see how built the part that does not work, buy it and just replace. (To be sure it is the correct part!)
t-mobile work with htc and they produce for them the phones so that the parts may have bought your phone from t-mobile will not be identical to that model which is not t-mobile.
Or just go to t mobile that will fix it .. they sure have parts for your model.