Where can I complain if I want to against a creditor?

Well well well, send those collectors in written letter, not to call you at odd hours, and they should stop.

For a thorough read on What to do if FDCPA is violated by collection agencies click here: https://wiki.debtcc.com/debt/fdcpa-rules-and-what-you-can-do-if-a-debt-collector-breaks-them.html.

It's a pretty good article from this site I found a few days ago... give it a read!!!

File a complaint with the state's attorney general. You can also File a complaint with the Consumer Financial Protection Bureau against the collector. They will investigate and penalize them for breaking the law. If they collector is guilty, you can get a partial refund of fees paid to a debt collector who has violated the FDPCA rule.