Contact the regulators
If the collector is "in any way, shape or form a bank," it has a federal regulator, says Smith-Valentine. "They actually take individual complaints and contact the companies about the complaints they receive."
"I always say that it should not be your first recourse," says Smith-Valentine. Only use this one if "you have contacted the company and received no resolution or response," she says, as regulators want to see that you've tried to solve it yourself first.
Again, opt for snail mail, she says. "You want to be able to send in copies of your correspondence, and copies of your return receipts, and you can't do that online."
One shortcut you could try is printing out the agency's complaint form, filling it out and sending it in clipped to your documents, she says.
States sometimes offer help, too. "Many times you will find that your state has a governmental agency that regulates debt collection in your state," says Smith-Valentine. "If you complain to them, they actually contact the company on your behalf."
Try your own state (as opposed to the creditor's state) first, says Magnuson. As a constituent, "you have a little more leverage," he says.