Psu(public sector unit) switching to hpcl

Sir I am presently working in a PSU. I want to join any oil based ongc company so I can earn more. For that they are asking for NOC (no objection certificate). When I ask my present 5 employer he is saying he won't give me. Because I am still under bond period only. I said I will pay the money after once I get confirmation of my selection from the other company which I applied. Still he is denying my request for NOC so how can I get. What way I should take to get that NOC so I can join my dream company