Insurance Claim, complaints?

How would I address a complaint with a very poor offer from a legitimate insurance claim? My house was hit by lighting and the roof was damaged. I contacted a roofing contractor and received an estimate as the insurance asked me to do. The estimate was just over 7 thousand dollars. The insurance company is offering me just 3 thousand dollars. They state that the roof shingles have too much wear and tear and that the THREE leaks are from that wear and tear, not the lighting strike. The House is only 12 years old and the shingles are rated as 30 years shingles. The leaks started the same day as the lighting strike. Any ideas how I can deal with them?