There is a disable feature at least on full size trucks, I'm sure it will work on yours to but I don't know if it's legal or safe to do. Your best bet is to take it to a dealer. There may be a tsb or recall we don't know about.
Most likely there's a frayed wire under the drivers seat. You're gonna have to look under there really closely at the wires. There is a procedure to turn off the seatbelt ringer in your owners manual, but it probably won't work because it involves buckling the seat belt.