If the 07 is similar to my 01, then there is a connector under seat that may not be having proper contact. I notice it happen when my wife drives it as she has to move seat forward. When I move seat back, seat belt light sometimes will stay lit. I can move seat back and forth maybe a couple of times and light will go out. I do not have a chime for that, just light. I am planning on removing seat, figure out which connector does this, I think mine has 2, and repair for good. Sometimes I can reach under seat with engine running and move wires a little and light will go out.
There was a recall on this one several years ago and supposedly taken care of. I purchased it in 2012.
2001 Elantra GLS 2.0