Telkom debiting incorrect amounts

I am sick and tired of Telkom debiting different amounts from my account every month with no explanation as to why. I signed a contract that specifically agreed to a debit order of R699 a month, however, Telkom has been debiting me over R1000, usually R1200, most months without any reason.

There was one month in which the debit was meant to be higher than usual, but this was expected. The rest of the times, they have simply debited too much for no reason.

Telkom is robbing me and I want to know why. If I do not receive an explanation, I will reverse the debit order that came off on the 1st, which was once again an incorrect amount.