Boys family can ells marriage after engagement

There was a boy who wanted to marry my younger sister so he send the proposal through various means... Since my sister was in 1st yr of MBA we refused but the boy pressurised.. So we thought to met the family and boy.. So with all meeting were done... The boys family came to our home to see my sister and they even told all the relatives that they are going for the engagement and marriage has been fixed. About which we were not aware.. So when they came they met my sister and after finalizing for 10laks Rs the engagement was done on the next day. My father told them that every ritual will be done on the same day marriage at one place and now we will not come to there city for any thing... They agreed.. But just after they left from out home. We started getting calls of how they didn't liked our welcoming and gifts and all. They asked my father to come to there city if he wanted marriage to take place. My father refuse d so they again called for some other reasons... So with the process of events now the boy called my sister that family have refused for the marriage. And now we have got the news that the boys family are saying everywhere that the engagement have been called of. We haven't received any call from there family and now they are looking for some other alliance with more money of approx 40 laks. So what could be the level procedure for that