@G23, you won't "both" receive a penalty if you "both" decline because only one of you will do the cancellation. If the guest cancels, the guest will have a monetary penalty. If the host cancels, the host will lose the ability to book the same days via AirBnB and receive a number of other penalties.
There is no way for you to both cancel. You can both *want* to cancel, but only one of you will actually do it.
To reach AirBnB, go to your Host Dashboard and choose the "Help" page.
At the bottom right of the "Help" page is a button labelled "Contact us"
Press the "Contact us" button to reach AirBnB.