Hello @Coll0
Welcome to CC,
There's much helpful advise here in CC.
May I suggest in future to ask the Guest to cancel, if you don't already, if they have an issue make sure you cover your own history in a civilised manner via Msg systems & suggest they use the Resolution Centre, then explain why you won't give a Refund, eg. is it mentioned in your listing or an unreasonable request & push either accept for whatever sum of monies they are asking, or "Decline" if you don't accept there request within good reason.
I tend to use the word "May" in my listing as that's a standard legal term & covers one's basis, e.g. It may or may not be available for breakfast choices.
Brush up also on Terms of Service conditions which we are also supposed to agree with when we use ABB
All the best
Central To All Home & LOcation