Charged for Upgrade and Promo fees -MTN Fails to pay after acknowledging it

i posted a review earlier this month with regards to an MTN upgrade done in April 2016 that i have been paying for and I did not have a device, looking for a credit for the device which I did not have. The analyst responded "We have picked up that cell number ******** expired already 2014-05-31. The line was billed for promo fee from June 2014 to October 2017 the account will be credited for the promo fee= R15,949.09 - the credit will be captured next week to the account." (nothing to do with the upgrade)this credit has not been done. Promo fees charged to an account, acknowledged by an employee. later that day another staff member calls to say that they will do a credit for the upgrade which was essentially not an upgrade. the credit was for 5000 odd and after making the October payment from that the rest of R3500 was credited to my account. My question to MTN and the analyst who is yet to respond is why is the the promo fee still being charged and why has R15 949.09 was not credited and no response from anyone at MTN!