Telkom debits my account but now blocked my account

Good day, I have been having a serious issue with telkom, I have a contract with them and they are doing their own thing they debit me on the wrong debit date and debit however much they feel suits them and now they have locked my account for non payment.. When I tell them that my account was debited they say it was debited by an external source.. So basically they giving my bank details to other people without my permission. The lady I spoke to was very unhelpful with attitude so I'm sitting with no phone now and no help.