It does not evolve by trade or level you need to take him to different places and never let it faint
Golbat doesn't evolve at a level it needs happiness.
You need to make it happier to evolve it.
It evolves with happiness. That means you have to level it up a lot and give it potions and stuff to heal it instead of taking it to poke centers. If you want more information on all pokemon go to this cool site called serebii.net it is very use full.
You need a lot of happiness for it to evolve