Confused

I had a car loan and was in a serious accident car was considered totaled and ins. paid but there was still a balance of 5,000.00. I travel for work and needed a new vehicle ASAP(rentals only last so long) so went got purchased a new car when settlement was over with ins. On my new car they financed me through a diff. company and I got my new car but still had old balance. Tried to make pmt. arrangement of 150.00 they denied it and wanted the original car pmt. which I explained I could not due my wifes health issues and to the new car pmt. So this account was charged off i had received letters from a collector who says he is an attorney tried again to make arrangements and again got denied the only arrangements made were to extreme for me to pay. I am looking into filing bankruptcy so I went through my credit report and saw it says Americredit (who held the first car loan) was charged off so looked for the collection agency and there is not one on my report. But when I looked at inquiries in March a Lawyers office looked at my credit report. Of course looked them up and it says they are a collection agency and they are good at sueing. I believe they are the ones that hold the collection. Do you know what I can do to get info.? Am really considering bankruptcy right now and dont know where to start on this. I really cant afford to be sued either.