Mtn and ssda taking chances

I had a contract with Mtn in 2012 and was paying them every month then I went into financial issues and went to 14th avenue to sort it out I don't know who helped me at the time as it was a long time ago but I paid quite a lot of money to Mtn to settle account and then I didn't hear from Mtn forever now I'm getting sms s from a company who is called Ssda and they are threatening me with a bill of 7300 I owe so I tried to phone them as rude as they are I simply asked them for paperwork they said they will send via mail still waiting for it now they have sent me another sms sayings owe 7800 now when I am asking for documents they now tell me it's not there problem I must get the docents from Mtn not them when they have been asigned by Mtn they dropped the phone on me I can't just pay 7000 rand to a company that I don't know what's happening and these people have all my details I have not been hiding our running away from anyone why did Mtn not call me about my outstanding to say this is what you owe please make arrangement only to be called up by this ssda company 2 years later if I need to go to court then so be it I will fight to the end my contract is with Mtn not ssda!!!