Not able to input my landline token

A month ago we bought 3 (prepaid) vouchers for our landline - all on the same day at the same time and at the same outlet - Ackermans. Went home and input two of them - and they registered - but the third one (R100), wouldn't be accepted by the system. Called Customer service; they looked at the landline account from their side and told us that they could see that the first two x R100 tokens were accepted; said we should "try again" to input the voucher the next day. We did - and same story - "Invalid voucher". Go to Ackermans - they call Telkom, who promises to sort it out. It never happened. We then called again; another session of explanation; another person taking the details. Told us that the technical department would load the voucher. Never happened. Try calling again: same run-around; same promises. Still no valid voucher. Still acknowledgement that only two were ever loaded. Still no explanation as to why the third one won't work. Had to go and buy another voucher - R250 - again now (without the first query being sorted out) and low and behold - EXACTLY THE SAME PROBLEM!! Cannot load the voucher - "Invalid voucher number". Now we have no airtime and no way of loading any!! TELKOM, PLEASE TELL ME WHAT THE HELL I NEED TO DO TO GET MY LANDLINE BALANCE UP AGAIN!