866-697-2399

They called I answered they had a debtor that I owed and they threatened me with a misdemeanor charge

You owed another debtor?  Owing money is not a criminal offense.

First, you should make a complaint at this Federal Agency, and while there you should also read up on how debt collection is supposed to work as well as what your rights in this matter are: https://www.consumerfinance.gov/

Also file a complaint with your State Attorney General's office.
List of State AG’s offices:   https://800notes.com/faq/attorney-general

They called saying they were trying to reach me to deliver some legal documents and that I would be charged $75 each time they attempted to contact me

Process servers get paid by the Plaintiff.  They cannot charge you because you "dodged" them or were unavailable.  This is an extortion scam using the fake process server tactic.

Call from restricted number, left msg on voicemail saying he was an "investigator" attempting to serve a court summons for someone (not me!) and referenced a "case number".  This is a debt collector, not a process server.  Just a scam to locate someone and get info with fake threats of legal prosecution.  Don't take any BS from these people and their shady tactics.

He called saying he was a process server and I was listed as a defendant. He needed me to call this number and ref **** said he would serve me wed. Such BS

Investigator Morris (female) going to serve legal documents on a certain date or we would he charged $75. They used my wife's name but referred to her as "him"

I tried to look up this number for Mr. Johnson (name he used).  Saying I owed money to Cash & Go from 2012.  It is now 2018 and they said they wanted to collect before time ran out.  I called Cash and GO after I told them I would check but they did not have me in their record.  Also, just curious but was told by C&G that I should always ask for a "Validation of Debt"  letter to be sent to me if I have questions about an old account.  Good Advice.  Big Scam they keep calling and leaving messages.....BEWARE!