Account problems

Hi ive upgraded 1st of Desember 2015 2 contracts,nrs *** and *** the first month I've noticed that the amout due was short of the amount i had to pay,then i thought that the account will be fixed end january,i called mtn call centre(mtn online) to bring the matter under there attention,i spoke to Devashen he is in the mtn online call centre in Durban,so he said thank you for bringing the accounts to his attention cause he was doing the upgrade,i saw on the *** contract mtn took 317 rand,whilst the contract was actually 249 rand,and on the *** contract i have to pay 317 rand,can you please help me to fix the contracts,cause i feel i was honest to phone mtn to tell them,Devashen told if i did not told them,this would have not been picked up,other thing is i dont want to get a surprise after the end of the month if they want to deduct money and there isnt anything left to pay,cause normally they deduct on the first of each month,i would really appreciate if [URL Removed] can help me.