- The guest needs to contact Airbnb, not you.
- Do not use instant book until you know what
you are doing and are an experienced host. - You cannot advertise for 4 guests and expect
People to see the fine print that guests 3 and 4 are children only, especially as you cannot discriminate on age (except not allowing children at all if your home is not suitable) so you will continue to have this problem so I don’t think instant book will ever work for you. - Spend time to learn what you are doing before you go live as you can’t rely on urgent messages on a forum (on which you did not state date of guests arrival or browser or device you are using to access Airbnb in your post).
I’m concerned that despite very step by step instructions on Airbnb website, you were still unable to cancel the booking, find a phone number, message Airbnb etc to resolve this issue. There are much more complicated issues ahead and you might need to hire some help until you are more confident and skilled at managing the basics. Something for you to consider.