I have been charged twice.

[Douwe8]

I have been charged twice for the same booking. 

How do I request a refund?

Best regards,

Douwe

[Fred13]

Perhaps best to contact host and if he received double payments, he can refund one of the payments. This would be a lot simpler than getting Airbnb involved.

[Mike-And-Jane0]

@Douwe8 Don't go to the host - Airbnb is fully responsible for collecting the money from guests. You can either call Airbnb or just request a chargeback from your bank.