First Federal Credit Control FFCC reported me to credit report yet can't provide me with invoice proving debt Cleveland, Ohio

I ran my credit report to see if anything was on it at which time I learned First Federal Credit Control had turned me over for collections for $100.

I called the original company where FFCC claimed the debt came from who told me that I owed -0- dollars.???? I then disputed the debt with equifax.  Equifax notified me some time later it was a true debt per FFCC.

I then called FFCC and spoke with "Paula" who was the most rudest person I have ever met.  I couldn't even get a word in.  She claimed the debt originated 5 years ago and they called me 3x and sent 2 letters?  They did have my home address but I never received anything.  I asked for an invoice so I can check with my health insurance company and see if they paid the debt or if it was my deductible and I had paid for it.  She said it would be "too much work to obtain that" I told her my company always turns over a bill when we turn someone over to collections.  She just said "when can you take care of this?" I told her as soon as I receive something showing I indeed owe that, that's when she got really, really nasty. 

I asked for a supervisor to no avail so I hung up and called back asking for a supervisor.  They put me through to "Rita".  Now when I made the first call to them I was put through to "Michelle's" voice mail and on that voicemail I explained I was calling from work and left a cell number for them to call me back after 5pm or if they weren't open  after 5 then they could call me back at my work number and left that number as well.  When I got through to the supervisor, I went through pretty much the exact same conversation with her that I had with Paula.  I told her I can't believe that I never received either of the 3 calls or 2 notices.  Her reply was "well we have called your cell number repeatedly and repeated the number I had JUST given to them earlier in the day.  I just got that number 8 months ago.  I had to argue with her that she had never called me on that number and the only reason she had that number was b/c I gave it to her. 

I told her I want to fix this but they were making it very difficult and I'm not going to pay something just because they told me I owe that money.  I don't even know who this company was that turned me over to collection.  Could it be credit theft? I'm not paying until I see a bill.  I told her she could fax it to my work and I will pay today.  She was so rude I don't ever want to give them a dime IF I do owe this. I'm not even going into everything that they said to me, but I don't want to be harrassed for a bill that I'm not sure I even owe!  I just want proof, they have to have something, right?