Incorrect billing and voucher ****ming

Telkom bills me incorrect amounts every time, they ****** me my accessory voucher when i bought a new device on contract, they said i will get it via sms but even now i have not received it and it has been 3 months. Chances are they took the voucher themselves.

When you call they say they are escalating it but never get back to you. I have tried getting them to debit correctly but each month they do their own thing.