Auto repair shop made repairs beyond the estimate dollars given by insurer. Shop wants me to pay difference, going to small claims.

Insurance sent appraiser, and estimate dollars approved was clearly stated. Final cost came in higher as Insurance pays out $34 per hour; shop charges $38 per hour. Difference was around $175, insurance paid about  of that. My wife signed a document when dropping off the car, but the document mentions nothing about it being CAR OWNERS resp., or that there was/would be a difference. The shop also said that this insurance company does this all the time (so they were aware there may be a difference in the end). Local repair shop wants me to pay difference, taking me to small claims.