Over charged by R15 0000

I have 5 contracts with MTN and each contract has a capped data limit. Yet on 3 accounts I was charged for additional data. The amounts respectively are R12 000, R2 000 and R800.<br> Last Monday I queried this and was informed that it was indeed a mistake and that it would be rectified.<br> REQ: *** but it was not.<br> Yesterday I called again and was told that the accounts department said that I am liable for the bill, The person that assisted me investigated and once again said that it is wrong and that the request would be sent to accounting to credit these accounts with the over charge. REQ: ***<br> My account still reflects the amounts as amounts due. What now.