Absorption of contract employee in Govt of India PSU

I joined a govt of India PSU in Delhi in November 2011 as a contract engineer initially the contract is for 1 years upto 2012 for foreign posting. But they further extended the contract agreement for 1 year as the project is still going on. Now on the 1-year extension is given every time, till now I completed 5 years working there as contract engineer and as the first phase of the project is completed they terminated all of us in July 2017 (there are 21 contract employee] and not provided gratuity and experience certificate. They provided experience certificate on [deleted]. Dear Sir,I want to add some point in the above question – 1. The absorption/regularization done in 2013 (who was internal candidate and 3 years foreign posting experience in the same company) 2. Company again given circular on 28.03.2016 (who is internal candidate and having 3 years foreign posting experience in the same company). 3. We have applied for the post as per circular eligibility criteria and under the apply date as per circular. as I am having 5-year foreign posting experience in the same company. I have mailed to HR division and CMD also to provide the status of the circular. After 36 reminder mail to the company up to 19th August 2021, Now company HR has mailed me on 19-August 2021 that you have been relieved from services of the company as a contract employee on 30.06.2017 due to expiry of contract agreement between yourself and the PSU company). Further, no recruitment process was undertaken in pursuance of referred circular dated 28.03.2016. Please suggest what legal action we can take in this matter and ask for permanent position.