Service agreement

I joined an automotive components company on 17th August 2022. They asked me to sign a service agreement for 3 years or 2 lakh, and I signed it. The signatories consisted of the HR representative name as well. She was not present there and she didn't sign. I thought she might sign in her chamber and she didn't. The other HR team collected the agreement and took it with them. After 2 years, I wanted to quit work due to medical reasons. I applied for a resignation. The HR team came in contact immediately. They started telling me to pay 2 lakh rupees. I asked them to send me a copy of the bond. They sent me a copy. I noticed a few things. It was not on stamp paper. It still had the sign of HR representative missing. When pointed out, they defended by saying they have digital copy where they have signed digitally. I asked them to give it. They refused to send it even after asked multiple times. I quit the job, saying it is not valid. They accepted the resignation and I served the notice period and moved out. They are now threatening me by sending legal notice and all. They have withheld my experience and relieving letters. I'm still not working with other companies and the job role given to me in office was different from what the HR communicated to me on whatsapp. What can I do?