8 months of overbilling and lying

We have had 5 phones with Rogers for many years.  

Rogers has overbilled us every month since last December.  Overchargin has have been as high as $200 overbilling.  Every month we spend time on the phone explaining, getting the charges reversed, and being promised it won't happen again.

One month ago I talked to a higher level complaint rep.  He "guaranteed" it would not happen again, however there was no guarantee beyond his word.  I told him I was leaving unless there was a concrete guarantee.  He promised that he would put a note on my account that if we were overbilled one more time we would get a $250 credit.  He would send me an email and hardcopy letter to confirm the guarantee.

Not surprisingly this was yet another Rogers lie.  Nothing appeared.  My wife has not been able to bring herself to fight with them any longer, and has not payed the last bill.  Their credit dept is now hassling us and threatening to cut off our phones.  Yes, we're leaving Rogers.