Property Encroachment

We have our property in our grannys name for 20 years now. She is no more now. We have our boundray wall on all the four sides, but we dont have land or property marking stone. Our negihbours now all of a sudden stating that we had build our boundary wall in their property which we know we have not. Since we have lost our dad they have started to harass us indirectly as they used to get scared of our dad. Our neighbours had build they house close to our boundary wall which we allowed them now they are coming into our property as they have put their AC compressor above our boundary wall and half of the compressor is coming into our property. Now we have a common road access us and the same neighbours, This road access was given to us by other neighbours to both of us. This negihbours are harassing us indriectly by parking their vehicles on this road and causing hassle and nuisance to us. What should I do to get all this rectified, the property trepasses and get the road access? Which chain of authorities should I contact?