Telkom poor service

Poor service from Telkom. Got a upgrade deal in March 2019. Old contract was never cancelled and the billing was wrong from the start. Deal was R249 pm but instead charged R505pm. Been phoning Telkom since June to get a result instead on 2019/08/31 was told that all the reference numbers given to me doesn't exist. Spend hours on the phone they don't want to cancel old contract and rectify wrong billing. Has stopped debit order. Tired of talking to unknown people who can't help you