truckergaz60

hi guys. I have a 325i se vert on an 07 plate. I have changed the interior for a different colour. since doing this the airbag light stays lit and the heater only blows through the top vents and only blows hot air. only thing I can see ive done wrong is the seats are not from my model. they don't have the lumber buttons and are not heated. the diagnostic keeps saying its the switch on the side of the dash but this has been renewed. any ideas would be welcomed. tia