Very bad contract

Very disappointed with the MTN contract took a phone in May I have to pay 590 per month have been paying extra towards the debt called on Friday to ask for the outstanding balance I am being told I can’t be given the outstanding balance as I have been paying extra towards my account so they can only see the credit balance I was told I will taken to the settlement department after that the settlement department tells me ‘my settlement balance is R14 000 I fail to understand how I am still on that amount , I asked if there is a statement I can get that has the opening balance with the payments I have made that shows the interest charged and my current outstanding balance