"Final Bill" not Final with T-Mobile

Went to local T-Mobile store to close my account and pay my final bill. Went in person so there wouldn't be a problem online. Was told I would not receive an additional bills, although I did. I asked specifically what was owed to close and finalize and when I got another bill in the mail, a return trip to the store, along with phone calls to "customer care" got me nothing more than "you owe the money." No wonder I wanted to switch carriers.