I just got this sorted in 10 minutes flat by calling them.
Please don't listen to people telling you to use email, or facebook or twitter etc.
They're a business, if they're not providing appropriate service you call them. Just google 'airbnb contact number' and Bob's your uncle.
People seem to think that if a company doesn't openly display a number it's somehow sacrosanct. That's not the case... they just don't want you to call them! They'll use words like 'emergency number' etc etc. The only 'emergency' a business cares about is enough unhapy customers to drive them out of business.
Trust me, they'll bend over backwards to help you once you get through to them.