Paid up letter

I am so dissapointed that this firm is quick to call a person when they have not paid up yet when you have paid and request the paid up letter, it is never sent! I am frustrated by these attorneys as they offered me a discount off my debt which i accepted. Now that everything is paid, i keep getting called to pay up the amount that they said theyre discounting me for. I asked for a letter from them so that they can stop saying i have outstanding money, of which I do not! Instead of assisting people get rid of debt, you help them incur debt! Sort out this issue!