How to return a device to T-Mobile?

I am cancelling my account with T-Mobile, due to terrible Internet speeds.  This is the only Internet system I have ever used where the download speed is lower than the upload speed.

Anyway, I got an email telling me that a return label was attached.  None was attached.  I went to the T-Mobile store and they told me they couldn't do anything for me because I didn't have the return label.  I called customer service, and they told me I had to work with the store to get the label.

So, now what?  The email tells me that I have 45 days to return their equipment.