Thank you for the response sm5275 brother,
From your experience,How much would be the reasonable settlement amount for me to pay/negotiate with  them?
I have consulted with some of my friends and Im getting mixed answers. Some of them suggested me to ignore the consultancy calls/emails and some suggest me to negotiate with consultancy like yourself.None of them have been through this exact situation like me.
Would there be any legal issues if I avoid their calls/emails? Or Could they contact my current client(employer) and cause issue with my job?
I have middle vendor as well. Can I just ask my current client(employer) to send termination letter of my contract to middle vendor? As far as I know..Consultancy doesn’t have direct contact with client(employer).

Thank you again