T-mobile will waive the cancellation fee if you call customer service and tell them you are moving out of the country and cant continue using their services in that country, or simply don't want to pay the internation fees. You will then have to go to a tmobile store and provide a rep with a letter stating that fact. The rep would verify your information and cancel your account with no termination fee.
I know this for a fact, because I did this when I moved to Japan for a summer.
Now it's up to you to create a letter or not.