Salut @Olga929,
Did your guest extend the 12 more days by alteration date request in the same booking?
or another new booking?
I apologize that I'm not clear-
" I was not paid by Airbnb. When I check stats, it shows that amount as paid."
Do look into the transaction history, you can find the complete payout, upcoming payment section.
Then go thought again with the update.
Do consider cancellation by the host will cost the penalty, effect the listing stars ratings and review.
Beside cancellation on short notice, the guest will be frustrating and troublesome to find a new place to stay.
Airbnb is a Trust & Safety platform