Hi @Jasneth0 whether you meant to or not, you cancelled, not the guest. You've fallen prey to a very sneak thing that Airbnb does (at least six posts about this in last two days). They encourage the guest to ask YOU to cancel, in order for the guest to recoup the service fee. If the guest cancels, Airbnb keeps the service fee. So the very bad solution that Airbnb has come up with is to provide guests with a way to email the host with an innocent request like "X wants to cancel, please confirm if you accept". You hit accept, and boom, YOU have cancelled, and now you lose in three ways 1) as you've seen, your calendar is blocked 2) you have an automatic review saying "this host cancelled the booking X days in advance 3) you are ineligible for Superhost status for one year.
Call Airbnb (and search on the forum for contact numbers, they are not easy to find anywhere else) and tell that that you do not accept, this was a tricky way to get you to cancel, you object to this practice, etc Or else do nothing and live with what has happened, and learn from this mistake. It's a crappy thing and tons of hosts are getting burned by this.