I am receiving a minimum of three calls a day from T-mobile's collection agency. They are trying to charge me a disconnect fee for stopping service 7 days before the end of the contract. They were unable to provide service in the area I was in. It wasn't because I moved, the service just all of the sudden quit working one day. I have e-mails and wrote operator numbers and dates each time I talked to them while trying to figure out how to fix the problem. It was because their tower just quit working. I was with out a phone for over two weeks when I decided to switch my number to another carrier.
If it is a third party collection agency you can put it writing that you do not want to be contact other than in writing pursuant to the FDCPA. You may have some state laws as well so you might want to talk with a consumer rights attorney.