Startek Limited Aegis - Salary Not Released

I joined Startek Ageis Kolkata as Operations Executive. Joined on **th June , and was under training period due to the health issues I left the company on **th July by informing the trainer and HR. During my entire induction and training period, they never told us to serve the notice period and when I left suddenly they came up with a new rule saying to serve one month notice period. It was neither mentioned in the offer letter. Several times I mailed them but there is no response. Please help me in getting my one month's salary. As you all know during this pandemic how difficult it is to survive. Hoping you all will understand my problem. Thank You.