Mtn helping themselves to my bank via debit order

In november mtn had a black friday contract for upgrade clients... For 150g the contract was R299. 00 that's it nothing extra. End November I'm charged R798. 99 which was confirmed an error a query was lodged everytime I went to the store I was told no feedback. Now we in January and I'm billed again for R519 for what? Mtn owes me money and they *****ing money from my account because they have my debit order details I will be escalating this to your ***** department. Immediately refund my money as I am done with you'll helping yourself to money that does not belong to yourll R700 is owing to me I expect this refunded to me Do not keep my money and debit my account monthly. I cannot believe a company like mtn would stoop to these levels to ***** from their customers.