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 checked this form, http://www.jotform.us/form/51675269633161 and the "Proceed to Checkout" button in the submit button of the form.
The user will have to select an item from the My Products payment field before submitting the form. Otherwise, the form will just redirect the user to the form's thank you message page.
Let us know if you need further assistance regarding this matter.