@Suzanne12, Never ever cancel a booking. For whatever reason YOU cancel, there are penalties. One of them is to have the calendar blocked.
If you have extenuating circomstances, you can call airbnb and they can decide to cancel without punishing you.
If you feel unsafe with a guest or there are other reasons why the guest is unsuitable, they can cancel on his behalf (even should he not wish to) and in this case, there are no negative results for you.
If you have a common accord in the message thread, call CS, maybe they flip part of the punishment.