Air Bag On-off Switch problems of the 2004 Volkswagen Beetle

In 2008 I took my vw Beetle to the vw dealership service department in murrieta, CA on date street and they have record that they fixed the air bag light/ and replace the switch which was lit up on my dash instrument panel. Well I took the same car 2004 vw Beetle back on 08/17/2015 at 8:15 am so they could take care of my airbag light which came on again at 107,000 miles. I understand that there are several switches from the seatbelts to the frontend and also behind the cars dash that can cause the airbag light to come on but, being this is a life saving part on my car I do not feel I should have to pay for a recall service and part on my return visit. As I see it this is a defect and a safety hazard and I should not be charged a $126. 00 to diagnose the issue and pay more for the part and service to fix a defective item. If I'm incorrect please advise me so I can understand how this is my fault. I thought if you fixed the problem then it should be on the company or persons who repaired the recall issue. Thank you very much and I would appreciate a response to my frustration with this issue.