Over Charging with payments

I was handed over in 2012 from MTN to Shapiro Shaik Defries with an amount to pay. I have been paying R250 each month since 2012/05/29... They charge me an extra amount monthly for Interest another amount for sms sended to me another amount for Receipting fees, clearance letters, consulting with debtor, phone calls wich they phone me... another amount for ordinary letters,facsmile or e-mail.<br> <br> I have been paying for 4 years now on an amount of R9314.24... I have reached an amount of R10 000 already and still owe R5013.90...<br> <br> They can't tell me where my contract for my MTN account is and MTN also don't know.<br> <br> What can I do in connection with this? I can't keep on paying for something that is been paid fully and extra..