There is a crack in my front windshield?

I recently had a rock crack my front windshield about 4 inches on the driver’s side near the bottom. I called some auto glass businesses, and I am confused. Even though some said in the yellow pages that they could repair the crack, over the phone they said the technology does not exist. One said he could repair a crack up to 24 inches. I am confused. I would prefer to have the crack fixed (not replaced) because it is cheaper. I am also concerned about if it is fixed will it be safe. Thank you