Front Air Bag Sensor Control problems of the 2000 Nissan Sentra

My service engine soon light was on for over a week. The dealer told me by phone to pull over if it started flashing. After the car was checked, it turned out it needed a " new mass air flow sensor". It was a Saturday so the service writer couldn't reach Nissan motor corp to see if I had to pay. I did call Nissan motor corp myself because the service writer told me Tuesday the service manager said I have to pay. The rep at Nissan motor corp spoke to the service manager and nthing was solved. Since I had a coupon, I did save over $200 but still had to pay $534. 07 on a 2000 car. I feel this is a safty feature that Nissan should not of made me pay for. I didn't purchase the car from this dealer.