Disgusting bill from MTN

My debit order for my mtn contract came off my account on the 1/04/2016, for R2365.50. I am firstly confused because my contract is R180.00 a month, I have app**** in the mtn store to have a limit put on my account, because this has happened before where I've had a disgustingly large bill and, this happened April 2015! The limit has clearly not been set. But I cannot understand this bill because my SIM card had not been in my device and I never have my mobile data on and I always operate it on wifi. I am also very upset about the customer care center! When I eventually got through, after a 20 minute wait, I was told that I need my SIM card number, when I told them I don't know it and I will be able to give them my ID number, the lady said no she can't do anything with that! I have already moved my cellphone contract to another network because of poor service and it's a shame since they have been one of the longest standing service providers. Now this month again I have been billed a ridiculous amount and still to this day have not received a phone call at all, I've just been told to go to an mtn store, by email! If feels as if No one is concerned or willing to help