Incorrect Billing

I have my contract with MTN for the last 5 years and am totally regretting my decision to upgrade and not switch back to pre-paid as per my original request.<br> Upgrade was done on: 13 June 2015<br> Trying to go from a higher package to a lower package has resulted into getting billed more then twice the amount and this is all due to the employee at the store not doing her job correctly! The 1 handset's usage limit was set to R1700 by her and I am getting billed to the extreme, paying for their mistake??<br> MTN has a ridiculous clause in the contract basically stating that the customer is liable for their mistakes<br> 2x Handsets with Insurance should cost me R466.00<br> The first debit for end of July was: R992.89<br> The second debit to be deducted end of Aug: R1298.86<br> I am extremely unhappy with MTN and will definitely never upgrade with them again<br> Please let me know what can be done to have my money paid back to me?<br> <br>