When I listed my room, I didn't change the extra charge for extra guests from "after 1" to after 2" so my guest was charged extra for their stay. How do I correct this? I see that I can issue a refund to them but I assume this is when they have already checked in and their card has been charged. I would like to correct this before their stay. Any suggestions?
I don't think you can make any changes once it's accepted. You would just give them a refund when they arrive. Maybe they will if you call Airbnb. 855-424-7262
Contrary to what @Cindy38 advises, you can still change the reservation.
Go to the reservation and you will see change/cancel; follow that, ammend booking, make sure you have the right total price incl. everying. Your guest sees that PLUS Airbnb fee and will have to accept.