If you have an Enterprise or Team account, please email firstname.lastname@example.org or call Billing at 707-399-8060 for payment options.
For individual user accounts, you can update your credit card in HomeSwingCORE.
Click on your username in the upper right hand corner.
Then to account on the left hand side, then "View Details" in the main window next to Add-ons.
Once on the Detail screen, you will see the transaction history. At the very bottom of that page is the Update Payment Source button. Below that allows you to cancel your subscription.