termination of contract without notice period

I am working with an organization (not for profit, section 25) since November 2012. It is not regular employment, there was a 3 year contract between me and the organization which got renewed in 2015. Now, this contract expired on 5th November 2018. Before expire of the contract, I requested the organization to renew it but, the organization did not reply to my email request for renewal. However, even after expiry of contract (5 Nov 2015), the organization kept paying me salary till now and I kept working. Now suddenly, they have issued me a letter dated 7th May 2019, saying that I will be relieved of my services on 31st May 2019. It does not provide me 3 months of notice period as written in the contract, which is expired now. Please advise, if the organization was still supposed to serve me 3 months notice period before terminating my services or what they are doing (23 days notice) is legally correct! Should I challenge them in court for not providing me 3 mon notice.