If you are using your device, open the Play store app from your device. Go to "My account". All your payment options should show up, including expired cards.... Tap "more payment settings". If you haven't been there in a while, you will get a notification that "our terms have changed...." (They changed in September, 2015....).Tap that. If you haven't already accepted "new terms of service", it will bring you to a browser page to do so. (I actually read it all, so I hit "accept")... Once accepted, when you go back to play store, under" my account/payment methods", you will still see all cards. Now when you tap "more payment settings", browser opens showing cards. Tap one. You can now either "edit" or "remove" it.
If you are using a pc, log onto your Google account. Edit payment options from there. I do everything from phone or tablet, so the first see the of directions apply...