Difference in oral communication and agreement

Dear Sir/Madam, I had purchased a flat in Mumbai region in April 2016. We were informed by builder company representative during negotiations that flat will be ready for possession by June 2017 and there will be grace period of 6 months. No agreement copy was provided to us before signing of the agreement at builder's corporate office. When I noticed this discrepancy once xerox copy of agreement were provided, I immediately inquired from the builder's representative asking if it is inclusive of 6 month grace period, he replied in positive. However this June 2018, I visited the property site again for checking on the delay, I was informed that December 2017 mentioned in agreement was not inclusive of grace period and grace period is actually 1 year and it was in force. So builder refused to pay the delay penalty saying they will go by the agreement only and refused to listen to any of my points. This leads to 1.5 year gap between initial committed date and revised date in agreement. As I am paying hefty amount as PRE EMI building being construction, I am incurring huge loss every month in the form of only interest payment on my home loan. I tried to reason with company representative saying I have the emails which make it clear that I was under the impression building possession by June 2016 as per initial negotiation. And this was all same till June 2018. What are my all available options to resolve this amicably without entering a long drawn legal battle? Please advise.