Nonsense collection company

This people harassed me for payments on 3 accounts i have with them. I paid up one of the accounts 3 months ago even now they are refusing to give me a paid up letter for that account. I am trying to obtain a settlement letter for the 2 accounts it's also a nightmare. They offer you a discount in percentages now i don't know how much i should pay and how. The worst part when you have to communicate with them it's a nightmare but when they demand to talk you even when you busy we don't give them the ******* attitude they give us.