I've been working for a US-based startup that has an office in India for the past 13 months. I resigned from my position last month and served the notice period even though my appointment letter didn't mention any such mandatory condition, the reason why I served it is because I needed proof of employment. After the notice period was over I was removed from all the communication channels and my official email account was deleted. They gave me the salary but didn't provide me any Reliving/Experience/Work letter, the reason they gave me for not providing it was that my performance was unsatisfactory.
Although my accounts are deleted but I've taken screenshots of the conversations that I had with my employer regarding the proof of employment. What can I do in this case?