Billing on cancelled contract

I have been trying to cancel my contract with yellow since September. It's impossible to get a hold them when you seek assistance, and when you finally do get a hold of them you get different answers from the various *********** agents. Eventually I spoke to a manager By the name of Miriam from the job branch who doesn't return calls and never emails feedback. Since October I have been being debited for something which I have paid for and cancelled. Today I get an invoice from telling stating that I owe money which has been already paid. Telkom is a bunch of ******* with *********** staff going right up to its managers. They have no customer s****s at all. Telkom contact me with a solution Acc no. ********** 72