If you really want anyone to take your claim seriously, you should start by telling us what your in-game name was, and the time and date you were banned. I also want to know the exact wording of the ban/kick message that you are seeing when you attempt to rejoin the server.
More to the point, you should not have been driving your car anywhere near the police HQ in Kavala, and if I had a penny for every time said "I crashed into XYZ by mistake", then I would be rich.
Further, we don't ban people just for crashing into cars - not even cop-cars. We ban because people KILL other players with their cars (or guns). This fact alone leads me to believe that you are not being fully truthful with your story, because most likely, someone died, and you've not said anything about that.
Alternatively, you were trolling, and it took a couple of minutes for the report to come in to whichever admin it was that used the hammer.
This is why I want to see the text of the ban message.