Telkom debit order rejection fee nightmare

Telkom mobile busy charging me rejection fee on my debit order if when there is funds in my account. i dispute debit order rejection fee every month, yesterday was debit order day, i see that they didnt debit, i'm expecting another rejection fee. they probably think its a new way to make money. i can wait for this contract to end, Telkom is so annoying i will never take anything from telkom even if its cheap.