Depends on how they paid, If credit card then initiate a chargeback against the tours and travels or take them to consumer court, its very easy to file the case online yourself. For the flight ticket unfortunately your only option would be to go to consumer court or eat the cancellation loss
I think not too much of a worry, banks have been on this site for a long time. They will only start devaluing if the amount of people abusing something goes past a certain threshold, if not they profit by all the people who cannot pay off the full bill each month but are chasing reward points.
IDFC wealth has a 2+2 or 1+1 offer where buy 2 get 2 free or buy 1 get 1 free if u book via PAYTM, 100% one of the best ones if you're going with friends.