Regarding Termination of employment

I work in a reputed cmm level 5 IT company, I was sent to the client side by my payroll company, I worked there for 1 year, now the client for which I worked has terminated the contract with my company, same day I received an email stating the same and saying that I have one month to handover the tasks and also after a month I will be released from my payroll company as well. After I visited them and asked them for some time, they said they are looking for clients and if I find some client I can stay else I will have to leave and say that its their company policy. They also sent me for an interview after which there was no response from their side. Later on, I got a good opportunity, got an offer letter, but now as the interview I gave also got cleared my payroll company is refusing to release me. Is it fair? Can a company do such things? Is it legal? Can a company revoke a releiving email notice?