Contract cancellation

Good Morning, I opened cellphone contract last year around Dec, unfortunately they didn't deduct Jan as agreed then I had to call them in Feb asking why are they not deducting? then they started deducting March i think then june I skipped a payment then they blocked my number, Mind due I was paying for the device without the benefits promised to me to date, I went to MTN witbank where i opened my account they said i must pay R1500 or so then i did pay it and it was not reconnected and now I'm loosing my client, money and contracts bcs of them saying I owe R7200 arreas and my instalment was R325 within a year i owe them R7200 how? I asked them to take their device and give me my number back as they are so useless and I honestly regret now my name will be listed unnecessary please help ***