Legal notice for not joining the company

Hi, I am working in IT field and was working in a company and thought of moving to another company for the career growth. I got an offer from one company and accepted the same. They told me to join the company in 60 days but our company notice period was for 90 days and explained the same and told them I will try to join the company in 60 days but cannot give guarantee on that. Meanwhile I got another offer from a different company and I was just in a dilemma to join which company. After serving my notice period I told the first company that I will not be able to join the company. And I joined the second company and now I got a legal notice from the first company that I was told them in the last minute that I am not joining the company and they are demanding compensation for that. In India it is very common that people will have multiple offers with them and finally will decided one of the company. I did the same and also there is no clause in the offer letter related to the compensation if the candidate decides not join the company. I have not accepted the legal notice and returned to them. How can I proceed further. Help from anyone highly appreciated. -Sridhar