Is it illegal to have a car with an illegal parking sticker and leave a phone number with the property management?

Doesn’t count.

The property management company manages vehicle parking in the community, and community owners should also regulate parking and comply with community parking management regulations. Owners who park illegally will be informed and their inappropriate behavior will be stopped. If an owner's behavior of parking vehicles indiscriminately leads to violations of relevant laws and regulations on public security, environmental protection, fire protection, etc. in the property service area, property service personnel are obliged to inform or stop the owner's inappropriate behavior by pasting notices or other means.