i was with tmobile and i had swtich to at&t and I had two lines on the tmobile. The second i shared with my sister and she was suppose to cancelled it and pay the last bill while she didn't and now tmobile is calling me and sending me things in the mail about it. I owe them almost 2,000 dollars now because of late fees n etc. Can someone please tell me how i am suppose to go about with this cause i really dont want this to haunt me for the rest of my live and just keep going up and up.