Charged an extra amount on my account for no reason and cant tell me what its for.

I was charged an amount of R338,99 on my account, with no invoice or reason. I didn't sign anything yet ADT take money from my account. Pure theft! I called the Rustenburg branch multiple times to enquire, everytime i was told that thru would call me back the lady is busy or some excuse, its been weeks now and I'm still waiting. Terrible service from theives