My company is not giving me my full and final amount?

So the story began on March 2024, I have joined 1 company for some part time project and we have signed the agreement.

In August due to some issues they have stopped the agreement and terminated me, and after the termination I have returned back their all the accessories like laptop and all. When I have asked them for my FnF the HR told me on call that it will be credited in my account on September, but in September when I called them they have mentioned that client has stopped their payment and once they will get it they will pay the amount. At that point I know they were just lying to me because the same client has other projects as well, so eventually the client should have paid the amount, but they are not releasing my payment.

I have mailed them as well, regarding this and regarding my paid leaves that they should have paid but they have replied me to submit my resignation from previous company and 3 months salary slip, I was unable to share these documents with them because as I mentioned earlier that I was working with them for part-time and was working in other company as full time employee and I have already mentioned the HR regarding the same before joining the part time company and at that point he was ok with that, but after the termination they were asking for these documents.

For last 5 months I was asking for my FnF on the WhatsApp but didn't get any reply, also they are not picking up my call..

How can I legally take action against the company?