Air Bag Light On problems of the 2006 Lexus IS350

Air bag light goes on and than off.

Takata recall- took my car to the Lexus dealership in honolulu hi for the recall on the passenger side airbag which they claimed it was completed and resolved. Two days later the airbag light on dash would blink. I called them to let them know and we made an appt. When I took the Lexus back they did a diagnostic test and claimed the drivers side airbag needed to be repaired at a $4,000. 00. I feel it should be repaired at $0. 00. If you can, please help. The service manager there is not helpful at all.