Employed in a company on probation period, company not giving salary

Hi I am working in startup it company, and I joined here in June 2017. I appreciated by client for good and quality work. Still i am in probation. I resigned and ideally i don't have to serve notice period but I did this cause my module is critical and I was the only one who handles this. I told my director i want to leave i didn't give the main reason cause he has quite idea and I don't want to mess with company and environment. In appointment letter on first page they mentioned after confirmation i have to serve 2 months notice period. And on last page they didn't mentioned probationery employee or confirm employee. And they are going to hold my last salary. Is this legally true. If you want i will send you appointment n letter scanned copy