Ok, so what the tech is telling you is correct, they changed manufacturers and the system will not recognize equipment from another manufacturer . I see a few options,
1. Bypass the airbag. I'm not sure how to do this exactly but I know people have done it in track cars. However, overriding safety equipment is never a good idea so this would not be recommended.
2. Go back to the original seats and safety equipment. Assuming of course the person you switched with is cooperative. They are most likely having the same issue on their end, just wether or not they care.
3. Instead of swapping the whole seat you could swap the components. That is remove the upholstery and swap just that. That keeps the original safety equipment and should not result in any errors. This is the more complicated and labor intensive route and also assumes a cooperative 3rd party.
4. If the person you switched with is not cooperative, you could purchase and swap the airbag equipment yourself. This however is very costly as it looks like they are approx $400 per seat.