When I first listed a room in my home, which was a couple of years ago, I created the listing and chose not to use Instant Book. However, the next day I woke up to an inbox with an Instant Booking and realised that Airbnb had somehow reactived IB. This is someting new hosts need to watch out for.
It's possible that @Ana1316 had something similar happen to her, or accidentally activated IB without realising, which is not that difficult to do as Airbnb is constantly pushing it at hosts on various pages, because it sounds like she was expecting to receive requests and enquiries before anyone booked.
@Shannon157as a host, it's important that you familiarise yourself with how the system works. Turn off Instant Booking if you're not prepared for guests to book without contacting you first. Keep your calendar up to date and block any unavailable dates. Read up on cancellation policies and penalties.
If you ever have a valid reason to cancel a guest's reservation (and not keeping your calendar updated is not a valid reason) or a guest asks you to cancel, call Airbnb, explain the situation and ask them to cancel it. If you are using IB, you can cancel penalty free if you feel uncomfortable with a guest or think they're going to break your house rules, but always call Airbnb about it first. I did this only two days ago with a guest who doesn't respond to any messages. You can't just do it because you got the dates wrong though.