Overcharging on contract upgrade

I upgraded my existing contract to a higher package at the Pavillion Telkom store. I was advised that there would not be any additional cost implications for the upgrade since I was upgrading to a higher package. I received a tax invoice early this month April which reflected that I was being penalized for the upgrade. I made contact with the call Centre and was advised that this would be rectified but to my surprise today my account was debited R11016.00 and my normal bill should have been approximately R2000.00 for the two unlimited contracts which I have with Telkom. I need this money to be refunded asap. The number in question is ***. The other number is ***.