Definetly a judgement call, @Rebecca330. I would send a request for money on the reservation as soon as possible. Also send a message to the guest that goes like, "I understand you are new to Air BNB and may not have noticed the extra charge for the third person in your party. I will be sending you a modification for the additional charge. Please accept and Air BNB will add that charge to your credit card. Thank you for your cooperation." Then wait for the response. If the guest denies that there was a third person or just ignores the request, your review would be a thumbs down based on breaking house rules. If there is a negative review, your good revviews will prevail and your response to the review should be able to clarify the basis of the negativity. Hope this helps.