Telkom overcharging me for my ended contract

Telkom are chancers! My contact ended on the 6th of October but when i received my last invoice, it stated the full month's amount! When I phoned, the consultant told me that unfortunately its because my contract ended in the middle of the month and not at the the end. So I basically loose out! I've reversed the debit order successfully with my bank and refuse to settle anything other than a pro-rated amount! Cheers Telkom!