Yatra Online review: trip cancellation

we booked a trip from yatra.com for Singapore as per advertised on their website and paid them the token money also. one and a half month after booking the trip a representative from yatra.com called me and told that our trip has been cancelled as the airlines was not fully booked. now what i do not understand is if airline is not booked then how it is my responsibility. it should be yatra.com responsibility to arrange my mode of travel. by cancelling my trip they have ruined my holidays. what these guys think of themselves? can you play with anyones feelings and emotions just like that? when you have promised something then they should fullfill it. i have paid whatever money they have asked me now where lies the problem. i need an explanation and resolution to my problem.