Being harassed by MTN and their debt collector's department for an account i never opened.

Someone did ***** with my ID and took contract under my name and i went to check today the contract was opened at Cape Town. Those people had all my details correct except my current address because they were using the some address from Cape Town. MTN tried to debit my account for the amount of R2200 and thought it was a **** and reversed the transaction and next month same thing until i went to the bank and was told its MTNService provider. I've called MTN and have been to their branches for help but have been taken from one pillar to the other pillar. now i'm being harassed by their debt collecting department VVM that call me to threaten me with putting my name on ITC if i don't pay. I've asked for the letter stating that i never opened the account and copy of ID, but still I'm being harassed after sending all those documents.