Cell c failing to generate paid up letter

I am Muofhe Makhavhu and I was a client with Cell c but I have paid them the outstanding balance and I have been calling them asking for the paid up letter but unfortunately I have not received it in about 2 month after full payment. There is a company called DMC that has been calling me saying I should pay my cell c account and as I call cell c they do not have any active account or any outstanding amount for me to call which means DMC if doing a *****ulent activity. Cell c Please rectify the issue with DMC as I do not have any outstanding balance. Please remove the *****ulent listening on my credit report.

Regards Muofhe Makhavhu