AMPCO Parking False charges of parking violations Denver, Colorado

Thursday, March 17, I parked in the Ampco parking lot over the Greyhound Bus station.  At 8:40 AM I paid for my parking receipt and placed it in my window next to another old receipt that was lying on the dashboard.  I flipped that old one upside down so as to avoid confusion for the parking agent.
 
When I returned to my car in the afternoon, I found a Parking Violation (# 48706210, issued by SAMUEL) stuffed in the crack of my door.  Since I remembered putting the receipt I was confused why I got it so I looked and I could see my parking receipt in the middle of the dashboard, exactly where I left it.
 
I went to work the next day and I ran into a coworker (name withheld, violation #701260881) who tells me that the exact same thing also happened to her a week or so ago. 

It appeared that their parking agent is simply not looking closely enough to the contents of the dashboard before he issues the citation. 
 
As evidence, I contacted AMPCO dispute office and mailed a copy of my parking receipt, on which you can clearly see the timestamp when it was issued.  I also included a copy of my bank statement that proves that I am the person who purchased the ticket that morning.  I mailed these in the the yellow parking violation envelope, and I also copied these objects to a PDF and sent them via email to the office. 

I contacted the dispute person via email: she said she would not be able to respond until she got the letter--which I thought was ridiculous because they say on their voice mail that they handle disputes "in writing" either "by mail" or by "email" to the address provided.  AND I had provided all the details necessary.  I never heard back from her.

Now I got a letter from a lawyer saying I have to pay the $75.00

This is clearly a shakedown for money.  I refuse to be robbed!