Telkom nightmare

Telkom has been the worst company I have dealt with when it comes to cellphone contracts. This month(May) my account was debited for R1014 when my contract is R543.dec they debited my account more than they should. They continued to block my line.. I called them only for them to apologise and say the money was not allocated. In February I also canceled my insurance but have been receiving sms saying I owe and I will be handed over.. Please assist as I have never skipped a payment and the interest keeps going up and up.. My name and credit record is being slowly damaged.