So I cancelled and Airbnb rental today online. It asked me for a reason, and I simply typed "We decided the stay somewhere else."
But I had to contact Airbnb, because the refund is scheduled to go to a credit card we no longer have. When on the phone with "J" from Airbnb, she referenced the recept, which I myself brought up at the same time.
Turns out I mistyped. Instead of typing "stay" I typed "shat".
And in case anyone cares:
To get the refuund on teh new card with the new number, you have to work it out with your bank. Airbnb can only refund to the original card number.
Also, if you have parital remaning payments on other Airbnb bookings, you can't manually change the payment card until you get a payment link email three days before the due date.