Guest Instant books for one night and messages that they would like a second night for free. :/

[Susan382]

I get an instant booking for one evening, and then a message stating that they would like to stay an additional night at no cost.  

I say no very politely, and he wants a cancellation (no surprise).   I cancel the reservation, and I get penalized by Airbnb.  

How can I let airbnb know WHY the reservation was cancelled? 

Are guests allowed to negotiate "free" night stays after booking your place?  

If not, then how are those guests reported?  

[David126]

Why did you cancel, should have just let them.

People can ask for anything, just say no like you did. Many discussions on her about asking for discounts and effectively this was what they did, bogof, odd to book then ask.