I never pay parking tickets; eventually the calls go away.. but...
Changing you license plate doesn't get you off the hook. When your new plate gets ticketed, it is entered into Impark's or the City's computer (yes, they have computers too); the very same one they used for your previous plate's infraction. Guess what? The two different plates match the same address and car make. Bingo! The files are merged into one. It doesn't take a rocket scientist to write code to plug that loophole.
Delinquent parking offences are contracted to collection agencies who are paid a "commission" to collect the fine by the city or lot. If they are unsuccessful, the ticket is returned and start to silently stack up against you. If you're a chronic repeat offender (the worst ones are lawyers, btw), eventually there will be enough fines accumulated to warrant pursuing this in the Courts. I heard that magic number was $1,000 at one time, but this may have changed.
If this ever happens to you, the only recourse you then have is to try to negotiate paying $0.50 on the dollar, directly with the City. The City usually settles for that, as their costs and time could well exceed that sum. Someday, I may reach that point, but so far all my past infractions remain unpaid. I usually interrupt the nagging collectors, and tell them I have already donated at the office. They go away eventually.