Cannot get paid up letter, 3 weeks now

MTN handed over my account to SSDA. I then settled it in full in August 2020 with SSDA. When I app**** for a new MTN contract now in April 2022 I was referred to SSDA by MTN. MTN is requesting a letter from SSDA confirming that account is paid in full/paid up letter. It has been almost 3 weeks now and SSDA keeps telling they are waiting for MTN to issue such letter. Each time I call or send an email I am told the letter will be ready in 48 hours. Now I am very confused as to who, between MTN & SSDA, should be clearing by name and in the mean time I cannot apply for a cellphone contract with MTN.