clamping down on LEGALLY parked cars

Hi all, i have a different kind of parking problem. My EC has recently introduced the process of placing stickers on illegally parked cars which has worked really well. The main issue we had was a people illegally using a small area that is clearly labelled “TRADE PARKING & LOADING ZONE ONLY”. However, a tradesperson i had at my home had a sticker placed on his car which still hasn’t come off properly. His car is a ute with an open tool box making it pretty obvious he was a tradie. My neighbour said she vaguely recalls some communications about registering renovations or tradespeople with the EC and i’m wondering if that is the basis for ignoring the fact that he was a tradie and putting a sticker on his  car anyway! The problem is the only method of contact the EC provides is an email address which is only checked occasionally.

So my questions are: do i have an obligation to register every tradesperson visiting my house and wanting to utilise this parking area? How is this practical when sometimes you don’t have enough notice of them coming out? If they expect this surely an email is not sufficient and they would need to provide a phone number that makes them contactable for the whole amount of time that they are policing this area?

Is the onus on them to prove the vehicle is ILLEGALLY parked or for the resident or driver to prove they are LEGALLY parked. If parking there requires prior permission even for a tradie that’s allowed there shouldn’t the sign be amended?

Obviously, there are things we can do such as putting a note on the car stating what unit they are working on and sending an email when its practical to do so but this is not a foolproof way of making sure this doesn’t happen again.

Finally, is there recourse against them if my tradespersons car has some permanent damage or if it costs him money to remove it completely?

Thanks in advance for any advice.