Pune Municipal Corporation — excess property tax

Address: Pune, Maharashtra, 411028

My father is stays in hadapsar. Other people in his society is paying 8000rs property tax whereas he recived 13000rs tax in 2017 for the same area. The flat is self occupied from nov 2016. Even though the pmc officer inspected, the tax came in excess. On visiting the property tax office they asked to give application and assured that from oct 2017 the tax will be adjusted... Since then we are continuously following but they are not doing anything. We again received 13000rs tax on 2018 even though we showd the flat to pmc officer to make sure tat flat is not on rent...
On asking the status they are just saying your file is under someone, if we call that person they are saying we are not finding your application or giving some other reason. My father is senior citizen and since past 1 yr he is trying to get the status but the pmc officers are giving some reason and the issue is still not solved. We have called so many people in pmc office and visited the office so many times... Please help what can we do...