Weltman Reinberg and Reese

I recently tried to settle a debt with Weltman, Reinberg and Reese. They split my payment into 2 monthly installments, and I willingly paid the first month. Due to circumstances out of my control I was a bit short to pay the full amount for the second installment. I called to tell them and said I could pay the full amount a few days later. The representative was short with me and said he would give me a call to "let me know if that was o.k". I can't give someone money I don't have, that's how I got into this mess in the first place. He did not return my call. So, after the allotted time, when I was ready to pay I still had not been contacted. I tried calling on two seperate occassions and the line just wrang thru so I ended up hanging up the line. Now the payment is about 18 days late, and they want to charge me an additional $205. Is this normal and fair. I feel like what is left of the debt is too small to contact my attorney and ask. Does anyone know what I should do?