Billing - Missing payment

I had an account with telkom mobile which has turned into a total disaster.<br> <br> The account has been handed over to nudebt management. I've settled the account with Nudebt management but they are still chasing me for a payment which i made in december (which reflects on telkoms billing system on the 04/01/2016) but nudebt has no trace of this payment. i called telkom mobile and advised them that the payment that they have on the 04/01/2016 is not reflecting on nudebt side and that they need to call Nudebt. No one has called nudebt and the payment is still outstanding. My credit rating is being affected as well as the payment is not on the account. <br> <br> secondly for some reason the banking details has changed and it no longer has my banking details on it and no one can tell me who changed it. I'm extremely upset and would like some sort of compensation as this is unacceptable. <br> <br> Could someone from telkom mobile please help me get this account sorted as my experience with telkom mobile has been a tornado!