Ripping customers off

MTN debited me double for the month of Nov due to them changing their billing dates and not informing the customer. I called them on the 21st to complain only to be told that an sms was sent, that same evening I received an sms apologizing for their inconvenience. I have logged two calls for a manager to call me to date no one ever called. My contract is up for renewal I am cancelling it. I have dealt with sh*t customer experience since 2003 it ends. I want my refund. a double debit just because you changed billing dates is not my problem. I should have been consulted before the changes were made. Failure to do so I will reverse the debit order.