sue them in a small claims court or something
Well-meant advice, I'm sure. But speaking as a not-entirely-uninformed person, I'd suggest that litigation is rarely a profitable exercise; and suing for small amounts is especially cost-ineffective. Among other things, collecting Small Claims Court judgment debts is a difficult and frustrating (though not impossible) process; at least, it is where I practice.
Notwithstanding the above, if you want to draft your own claim and represent yourself, it should cost much money, and would at least get their attention.