SSDA HORRIBLE SERVICES WITH ATTENDING TO CUSTOMER QUERIES

What must a person do to get a paid up letter honestly, it been 3 months since I settled payment for my Cell C account handled by SSDA and I have been querying for it but no feedback. This has resulted to the account appearing as Adverse record on my credit report. This is so frustrating and resulting as horrible service. With Norman Bissett & Associate Group I really did not have this frustration yet I settled their account after settling with SSDA