Harassment by Neighbors

We live in a housing society. There used to be a public pathway adjoining the compound wall. A family on the other side of the path encroached on this pathway, moving right up to the wall many years ago. The municipality took no cognizance of this. These people then began harassing us, throwing all their garbage over the wall and getting very abusive when we asked them not to - shouting loudly and gathering a mob is their favorite technique. Their logic is that just because we live in a bungalow with a large garden space, we have to put up with their garbage-throwing. They complain about our garden trees and the woman even said she was going to get 'someone' to cut these down. Another reason for quarreling was their habit of setting up Mandap poles during ceremonies into our compound without asking our permission. After repeated complaints to the municipality, the garbage throwing has lessened - they still throw something every week to harass us and their children throw stones and things into our terrace. We complained to the Nagar Sevak and he spoke to them. They have not stopped this behavior. The man is verbally abusive. In the past, he had threatened to 'see us in the street' and used to make abusive comments every time we worked in our own garden - when we swept the garden, he used to say 'the Bhangi have come, the Mahar have come'. He also goes on and on about being 'a Brahmin just like you'. It is stressful to have to put up with this. Talking to them does not work at all. What do you advise? Will making a fresh complaint about their encroachment have any effect after all these years?