Your airbag light can be on for a numerous amount of reasons.
Number 1. Your module was not reset.
If you had your seat belts repaired but did not have your airbag module reset your airbag light will still likely be on.
Number 2. Your seat belts have not been repaired.
If you had your airbag module reset, but did not have your seat belts repaired your airbag light will be on.
Number 3. You need to clear your DTC codes.
If your module and seat belts have both been repaired and your airbag light is still on odd are you need to clear your DTC codes. You can do so using an OBD2 scanner.
Number 4. You have a faulty connection somewhere.
When connecting seat belts and airbag modules, please be sure to have a solid connection. A loose connection will make your airbag light turn on as the resistance will be too high.