how to leave a good customer service review?

Id stay away from mobile service like T mobile services and them all together rude customers service if your no longer s customer of thiers they only care about u when your giving them money. But if you switch services from. Them they send you bill after bill raising the amount by 7$ for a one time charges. But send you a bill again the next month as a reminder but also charging 7$ dollars again and calling it a one time charge. We'll if that was true that it's only a one time charge it should of been only charged to my last bill one time. Plus my last bill was the 11th they waited 6 days and sent me a new bill with a larger amount on the 17th. 6 days only waited 6 days before charging me. After I just switched services. So if yea they only care about you when your an active customer but once you switched they could care less about you. So be careful. And when you try and talk to customer service and tell them you no longer with t mobile thier attention and attude change instantly. Evan thier head of customer service is rude and don't care to talk to ya. So as long as u a customer you straight