They don't want to give me my paid up letter poor customer service

I had a loan from FNB that i was paying them through Anders Inc Attorneys in 2018 April spoke to Nonsikelelo Zulu from Anders she told me that we need to make arrangements for 403 per month that we be paid for 24 months without skipping amonth i will be qualify for a discount i have been paid the same amount since April 2018 until April 2020 . Early in May i called them and i spoke to Christine i told her that i was asking for a paid up letter she told me that she will ask it from FNB when she get it will come back to me i have been since calling then they promise to come back to me but they don't do it sometimes they hang up the phone promising to be transfering me to the person i ask to talk to i called FNB asking for a statement their told me Anders has not updated my payment it shows that I'm still owning them i also sent them e-mail 3 weeks back they don't reply my e-mail