what do you mean by not function? Spoil? Or just as simple as out of battery? Or slightly more complicated, the dunno what called, "ultrasound code" out?

You just need to bring it to any key maker in shopping mall, ask them to check if battery flat? If yes, simple, only replace battery. If code out, then, pray one of the key code still ok, then, ask them to reset. Both cost also definitely less than 800

If not, than, either you bring to Suzuki to change (cost u 800) or you go to any car accessories shop, say want to change car alarm, got cheaper version one. But, your car warranty void, if there is still any