Help!

Hey people! What do you do when someone books your room to move in, pays you the token amount (non-refundable) and backs out a day before move-in saying they found a cheaper place? Then they come back 3 days later with an entitlement saying they want to move in again in the next 5 days or want their money back after you finalize someone else and your entire timeline is shifted plus your time and efforts are wasted. Is this ethical?