Unpaid maintenance since last 3 years

Hi I got a divorce in 2009 on mutual consent. My ex husband was liable to pay 3lacs a month as per our decree. Since the first year i.e 2010 he has never paid me a full amount of 36lacs a year infact there have been huge discrepancies in the amount. I did not raise a question then becuse we after divorce were on a very friendly terms and frankly speaking 3 lacs a month for me was way too much. After 3 years i.e in 2013 he reduced the amount to 1 lakh verbaly stating that he wasn't doing that well professionally. I agreed to him as again we still were in very friendly terms. In 2016 he reduced that 1 lacs to 50000 again using his bad professional life. In 2019 he stopped paying me that 50000 as well saying I don't have a job and will start paying you back when I start earning. By end of 2019 I got to know that he has been lying all this while and travelling the whole world , staying in 5 stars, having lavish dinners, giving expensive gift to his girlfriend. As per my decree the settlement can only be terminated if I give it in writing that I don't need it. I in anger and frustration sent him abusive whatsapp messages and told him to keep his money to himself as I don't need it. I am financially not doing well infact I am surviving on the interest of my savings which is very less. Now when I had sent him a legal notice to start paying the maintenance he is saying the agreement stands terminated as I have given it to him in writing via what's app that I don't need his money and says that we have had a mutual understanding that he will pay me 3lacs for certain period of time then slowly gradually will reduce it and finally end it when I would be in a stable and better shape though our decree doesn't say so at all. What should I do?? Please help me as I am going through a real tough time.