Bad service and support from MTN to sort out incorrect billings

I upgraded my contract at Northgate at the start of January - and was promised by the sales consultant that my first two months of subscription on the new contract will be for free. Subsequently - at end of January - I followed up on this - and was told that this is not showing on the system. The customer support agent logged an incident ********** 72 to get hold of the branch and confirm this - so that the account could be sorted out. I have now received the invoice without the discount for the first month, and upon following up - I was told to rather just go and sort this out myself with the store. This is not acceptable service - I was promised that MTN can sort this out a month ago already - but no further focus was given to this from your side - apart from logging an incident for this. When asking to talk to a supervisor - I was told no one is available - but that they will call me back when they get notice of my escalation. The consultant was not able to provide me a SLA of a supervisor being able to get back to me on this - which is also not acceptable service. I also asked the consultant to log a dispute on the account - as I will not pay this - the amount is incorrect. Incident number ********** 05.