The Billing and Teams dashboard allows you to enter and save new card information:
The user responsible for billing on your Streak account can add their credit card information before the trial ends to automatically upgrade to a paid plan on the last day of the trial.
Click the Streak icon in Gmail's top bar
Select the Manage Billing and Teams option at the bottom of the sidebar
Scroll to the Payment Method section and select Add Credit Card
Enter your new credit card information and confirm with Update Card
If you have any problems entering your credit card, just let us know and we'll be happy to help you.