Possible theft

This month I was billed an amount of R1900.00, please note I have a 2GB contract for an old ipad I have stopped using for a few months now. Uppon calling the call centre I was advised that it is for "high internet usage" I asked the lady how can this be as this ipad has been stored away due to the internet not working for a few months, I also asked her to cancel this contract, to which she then said that the high bill is for high internet usage for the month of 26/06/2017 up until 27/07/2017, so why was my account dedbited now??? she was unable to provide an answer, when I told her to cancel this she said, that I called on the 27th of July to cancel! I advised her I never once called MTN as I have stopped using this bundle and used to the normal amount I was charged for the bundle, she then corrects herself and said a lady allegedly "suspended" my account as she could see "high usage" that was irregular and suspended my account, allegedly she sent an SMS to say my account is to cancel it, which I never received, the agent confirmed its a miss Van Wyk who suspended my account if not mistaken, I want to know why is this being charged now and I want this contract cancelled asap and to be refunded, calling your call centre proves no help whatsoever, I also requested a billing analysis and demand to know why was I charged R1900.00 now for something that MTN states is for the month of June and July?? Please send corrispondace that this will be cancelled (the contract is over two years old.