What should one do if falsely 'referred to a collections agency'?
Legally there is an action informally called "slander on credit" in this status if you decide to move forward you can sue the credit reporting agency and potentially the creditor and parties that reported the debt, basically on a defamation complaint. Not something most attorneys would recommend an it is rare, and honestly very hard to prove. Second some people will suggest to threaten but not something most attornies would suggest.
Consumer affairs or Better Business Bureau is way to file a report them to the online or in person. You can also write a bad Yelp review,tell all your facebook friends, and otherwise flag their bad behavior, even file websites to complain about their incorrect activities. In these posts you can tell them they'd better stop the defamation/sabotaging your personal finances on a false claim. But one very important manner to remember. You must have actual facts because if your facts are off or slighted you're defaming them each can bring expensive legal fees.
In some cases I have made suggestions to friends or colleagues to make them a small cash offer in exchange for a them to report to all 3 credit agencies that the debt was placed incorrect and that they should remove it from your record as a good faith effort. This type of reporting is not the same as reporting bad debt or debt is settled or payed in full, which would leave a score your credit in a negative way against on your personal credit score . The credit agency admitting that the debt never existed or that you had no fault with this debt.