I Racked Up Thousands Of Dollars In Parking Notices From Parking Revenue Recovery Services. What Now?

I had recently moved to a new apartment in CT in September without designated parking. There was a parking lot that was close by that had a car with weeds growing around it and garbage bags in the windows so figured no one checks it. For the next couple of months I parked there and never received any tickets or notices. One day in November, my friend who has also used the lot sent me a screenshot of a notice he got for $89. My heart sank. I went on the company website, typed my car info and to my horror I owe nearly $7,000 in parking notices. A few days later I got a thick envelope with the paper notices in the mail threatening to take this matter to collections if I don't pay the amount. The messed up part is that they documented every day that I didn't pay, but they didn't send me any bills until November which is when they processed all of the notices at once in a single day. Full disclosure there are signs in the lot about failing to pay for parking which I regrettably ignored, but I thought it was a city owned lot and that I would get a ticket or at worse my car towed. I know I messed up and I know I was in the wrong, but what should I do?