Trying to settle a claim with USAA and they stopped returning my calls and emails. What should I do next?

I was a passenger in a car that was at a stop sign which was struck by a van illegally crossing with traffic moving. He was tboned onto our stopped vehicle, totalling the car and giving me and my friend concussions on August 9, 2013. I had to drop a class because of pain and attended a few months of physical therapy. My bills came to $7,000 and USAA offered me $8500 to settle. I told them about the extra semester, the missed graduation date, the time my bills have been in collections, and the job interviews I have lost because I am still in school. There was no fault on our part and now I have a daily routine to help my neck and head that seems required otherwise I have trouble sleeping. I don't know where to go from here.