JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
You can do in the Billing/Payment section when logged in to your account.
Here is the direct link https://www.jotform.com/myaccount/billing
Click on the Change Credit Card button on the payment section to open the update information window for Billing details
See the images below for guidance:
Let us know if you need further assistance.