T-Mobile USA review: Charged for internet router that I returned and they can't find!

I canceled their service 3 months ago after at least 5 different calls to various branches. I had to go to a store verify identity ect. Finally got my number ported, returned their router & was assured I was canceled from all services with no outstanding balance. Then my acct. gets charged for the router I returned because they can't track it down?! Spent approximately 1 hour on the phone arguing with them, they agreed to credit my bank account for 244.94 in 5-10 business days. I'm still waiting on day 12. This is a very sorry situation that should have never happened. Do not trust T-mobile no matter what they tell you, they lie & do not follow good business practices!