What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
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.
I think that this is not possible, I made some tests and though you are able to edit the submission it is not possible to edit the product already purchased since your customer has already paid for it.
The only way to update payment info would be submitting the form again and purchasing a product again filling the form with the proper info.
If this is not what you're looking for, please provide us a bit more and we will be glad to help you.