How do I fight an innacurate police report and insurance claim stating I am at fault when I know I am not?

Question: I got into an accident on the highway which clearly was not my fault. A car had basically lane changed into my lane while I was changing lanes as well but I began the lane change first. The police report and both insurance companies are holding me liable. I would have swerved back out of my lane but there was already another vehicle pulling up from behind blocking an exit path. What can I do here?