Employer terminated me without notice after I joined a union?

Hello, I am from Ahmedabad and was working with a manufacturing company for 2 years. Last week, I decided to join a workers' union and informed my manager about it. Yesterday, without any prior notice, I received a termination letter citing performance issues. I have always met my targets and have positive evaluations. I am worried that this sudden termination is due to my union affiliation. What are my rights in this situation, and how can I challenge this unfair dismissal?