From the web: Visit My Vinli at my.vin.li and login to your account. Click your account name in the upper right corner and select “Edit Profile” and “Billing”. You can replace the card on file with a new card or delete the current card.
From the app: Tap the menu button on the bottom left corner and select your account name. Tap the “Billing Info” tab. You can replace the card on file with a new card or delete the current card you have on file.
For T-Mobile Account holders, you will manage your payment information under the WIFI settings. From the app, tap WIFI and then Purchase. Tap the "Manage My Subscription" button and follow the prompts to update your credit card.