Pending Municipal/Property tax old owner refuse to pay.

Hello Respected Lawyers, I recently purchased (Stamp Duty Registration date May 2016 on my name) for my own stay a re-sale property in Mira Bhayandar Municipal region (Thane district - Mumbai), this is registered Co-op housing society and recently all our society member received pending property / municipal tax. This tax receipt has Total amount and also a section which shows amount per year and on calculating, this bill is for 3.084 years. This bill is generated by MBMC on old owners name and as per Government records, I registered for this property legally on 08.May.2016 and payed all the legal taxes while purchase. I calculated my liable dues starting May'2016 up to the end date of the Bill i.e Aug'2016 and informed the old owner that I can pay for the period I legally registered for the property and I passed this MBMC bill to old owner and the old owner is denying to pay this property and is saying that "This is your flat.. you take care !! I sold flat to you.. You cant ask for me to pay !! etc etc.. " and ignoring me. I revisited my housing agreement and there in point no. 11, its clearly written any society dues, Municipal taxes are liable to pay by seller before day of registration minus one. Please advice what is the legal way to solve this issue. Awaiting your valuable answers. Thanks, Responsible Indian