Double charges

Multichoice is giving me the bad service ever, in 2015 i bought my decoder it was a compact it was perfectly working good because i was paying on time and at the store, now this year may i wanted to upgrade to Explore, i made the call and Fortunately they offered me a special for R499 per month price lock for 24 months.Ever since i received my package I've been fighting with them every month. First month they deducted R780, june R499, July R800 now today is the 29th they switched it off and they say im owing R790. I really dont know whats going on as this is a debit order arrangements. Is not even month end but my decoder is off and ive paid more than i was suppose to pay.please assist me Kind regards ***