Region Service Co Inc

I just had this company come out on Sept 27, 2013 to re certified my heater and was told that the fifth chamber was bad. My heater is only 7 years old and was advised that the guarantee for the chambers are only 5 years old. It also would involve taking the heater apart, and could release carbon monoxide or possibly a new heater. I had another company come out on Sept 28, 2013 the next day, and the service guy checked all 5 chambers, 3 times and all of them were working condition. What would you think? The only reason I checked one start is because I had too, not because I wanted too.