Consumer Redressal

My model no is Mi-516, its under warranty period.I am facing the problem that the mobile's shut down button is not working.I have given my mobile to the Spice authorized service center Billenium Sales and Service(P) L, Brabourne House,6 Chowringee Lane on 17.01.2014.They have been giving me dates after dates that my mobile's problem is resolved, but yet today the problem is there in my mobile set.Today they have been telling that my mobile can't be repaired. It has created a liquid damage which can't be resolved. What the hell is going on the service center, they have making me wait for 20 days and harassing me and now they are telling me that the mobile can't be repaired.They have been sending me messages after messages and telling me that my mobile is repaired , but when i am visiting there they are telling me its not their fault its their head office's fault.