Front Air Bag Sensor Control problems of the 2000 Mazda Protege

My check engine light began coming on in June 2003 and they replaced an oxygen sensor. My car was fine until recently. I had an oil change in April and the light came on again, but it only lasted a few days. Two weeks I had an oil change and right after the service the check engine light came on again. I called the dealership and complained that the light came again after they serviced it. This makes it twice that I had my car serviced and the light comes on. Also, I was never informed about the recall in January 2001 about the breaks. I had brake service done last year and I was told I needed brake service again.