Auto accident from December 2013

I was involved in an accident in Dec 2013 where a woman hit the right side of my vehicle when I made a left turn. The police were never called and I didn't have insurance at the time. I gave my information to the other driver and heard from Bell subrogation (a collection company for State Farm) shortly after. I set up a payment arrangement with them and paid several thousand dollars including a down payment. I never received a copy of my agreement with them though they claim they sent it. I recently began paying lower monthly payments because my son died and I haven't been working. Now they say unless I pay another down payment again to set up a new arrangement, they'll pursue the matter further. I'd like to find out what my options are.