MTN LINE SUSPENDED

I have a contract with MTN and seems that the amount that I'm owing does not match the amount that I originally signed up for. I phoned and I was told that I have an outstanding balance of about R13000.00 I shocked to hear that, however they suspended my line and know struggling to get my services active again. When I opened, the contract I was told I will only pay R250.00 no extra charges. Please urgently assist me in this regard