Overcharged on Data bill

I have been charged R1800 on my data ****le account - apparently having gone over by 3 gigs, which is impossible. Accounts department haven't been helpful at all. I have heard of numerous people who have been overcharged by as much as R3000 on their accounts, apparently due to a \data leakage"of some sort. Please contact me asap otherwise I will be forced to take my business elsewhere. I have been a loyal customer for 5 years."""