Cell C paid up letter

I had a contract with Cell C and the account was handed over to SSDA(Shapiro Shaik Defries and Associates), 15 November 2021 I settled the account and was told to wait 21 days before getting the paid up letter, I've been calling them both SSDA and Cell C to provide me with the paid up letter ofwhich none of them is willing to help and my life is stuck I can't do a thing because of them. Kindly assist me.