Paid up letter

I was handed over by CellC to ssda because I had an account with CellC ,then I settled the account in 2022 June. I have been trying to get a paid up letter since then to date. The company that I was dealing with told me they are waiting for CellC to send it to them ,but nothing. Since then I've been calling CellC myself but still getting empty promises, I really don't know what to do. It's 6 months already and still nothing. Please help me.