Automatic discount from airbnb

[Yamen0]

well, i had a discount on my booking for 30% of the total which i never set up this discount option,,, now the booking is reserved because i didnt expect such a discount and it never happened before. had to ask the guest to check the rates again and maybe pay the differece but they didnt accept that. im thinking of canceling the booking but im going to lose the guest and days will be blocked. any ideas ??