Paid up letter request

I bought a phone in 2022 around August, I bought it via mondo using mtn. Fast forward lost the simcard and didn't pay, I was then taken to Ssda lawyers who I started paying. I completed paying Ssda and when I asked for the paid up letter they referred me to mtn and only given me a balance sheet. I've been requesting a paid up letter from mtn and they have been giving me the run around, please asssit me in exposing them for their bad customer experience because now they are blocking me as it stills says I am under debt review and I paid them of in January