Be sure to check your junk mail inbox. If the email did was not delivered I would suggest contacting them again as that is the best way to be sure to have this resolved.

The message may have been sent to junk by the email client you are using. 

Return through the mail

1. To begin this return process, contact us. If you're a T-Mobile for Business customer, request a call​ instead.
2. We'll send you a prepaid return label to ship your device back.
   • Don't worry about a shipping address. Our prepaid return label has that covered!
   • Labels usually arrive in your email within 24 hours. If you don't see it, check your folder such as junk or spam.
   • Print the label, and attach it to your shipping box. If you can't print it, a T-Mobile store or print shop can help.
3. All you'll need to do is pack up the device, and drop it in the mail or take it to a UPS store.