Worst customer service ever!!

This would one of the worst customer experience moment ever! I have been overcharged for awhile after I moved you all kept charging me for my last address until I caught it. Had to call in and wait a long time to get on a the phone with a rep. Then they proceeded to tell me that they would not reimburse me but pro rate the amount that I was overcharged but only by 3 months but I have been paying much longer than than. So I'm leaving you all for AT&T. Of course I become a valued customer whenever I 'm leaving but as I'm trying to cancel my service you rep hangs up on me twice and then tries to sell me on a new promotion that will give me better speeds at a lower rate. You know if you want to value your customers' xfinity you should just switch them to the lower rate and better service rather than just wait for them to notice that they are being over charged for their current service. You all need to work on being a company that cares about their customers or you will be non existent in the future.