You complaining to band A about band B makes you look like you're one of the bickering girls as well.
You should just go to their show and talk to them straight out. Tell them what they owe you and why. They are obviously amateurs and morons, but crying about them to their peers is only going to make you look unprofessional.
Good luck. At least next time around you know that if you're dealing with amateurs, you need to treat them as such and get paid in full up front.