Service suspended due to billing errors by Telkom

My service has been suspended because apparently "I am over my limit". If I log into their portal it shows that my payments are up to date and the next debit order will be R675. I went into the store and they arranged that someone would call me back to solve the problem, but I never received a call. When I call their call centre, I am told that I owe an amount of about R5600, but they cannot send me a bill, and they cannot disclose what the services were for. The amount is "just there" for whatever reason and Telkom themselves cannot even explain how they arrived at that amount.