Carlen Chevrolet

My truck was involved in an accident which was not my fault--other insurance company was to pay for repair work. I took the truck to Carlen Motors in Cookeville, TN for an estimate. They gave me an estimate of $1915.23. When they repaired the truck, they charged $2567.79 which was $$652.56 more than their estimate. The estimate states "Clutch Is Open" which means if they find other problems caused by the accident, they are to call insurance company for supplement. A CPCU Leader (Chartered Property Casualty Underwriter) from the other insurance company said he told the the repair shop at Carlen Chevrolet if they needed a supplement for any extra repair work to contact him. The repair shop person never contacted the CPCU Leader which caused me to be out the $652.56.
I have all the original paperwork which I took to the owner of Carlen Chevrolet to look over. He was supposed to check into this and call me back; but he never called. The office girl said they would not pay.
My truck had very low mileage and the clutch and brakes were working fine prior to being hit from behind by another person.
It was not right for Carlen Chevrolet to fail to get a supplement causing me to be out $652.56. I believe Carlen Chevrolet should pay me this amount.