Ex Property Manager Sent Bogus Balance to Collections

[James G.]

I let go of one of my property managers and had $0 owed to them- they sent a $6,000 balance to a collections company. I called the collection company and told them that the balance was bogus, and they said that I'll have to send a letter to dispute it, but that the collection would still go on my credit report. Does this mean that any Adam on the street can send a bill to a collection company and it will go on your credit...?? How does one fight this to ensure that it doesn't affect your score? How do you deal with the collection company and how do you deal with the issue as a whole?