Double Billing two months in a row

Renewed contract in October 2015 and have been billed for old device and new device two months in a row, logged the complaint and 4 weeks later still waiting for first months over deductions to be reimbursed. Again this month same story, call centre consultants says queries must be sent to back office for investigation first even though they can see I was double billed again. Pathetic, wont be taking up a contract with Telkom again, actually thinking of cancelling my contract as a matter of fact.