Billed for a free phone and unable to log dispute

I recently moved from Potchefstroom to Centurion and so requested a line migration for my fixed telkom line. This was done without any problems and I received a sms to inform me that I am eligible for a free cordless phone. I went to pick up the phone at the Centurion mall Telkom Direct Shop and was again assured that the phone is free. However, after receiving my monthly bill I had been charged for the free cordless phone (R439.00 vat incl.). I returned to the TDS to rectify this and they logged a dispute. It seems though that the dispute system is not working, since the dispute does not reflect anywhere. I have also logged a dispute with no success. All I want is a credit refund for the supposedly free phone.