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 have checked your form and I can see you have already set up a mask to the phone field:
There are also some widgets that will help you to capture the phone number and apply a format based on the country or region selected, here're the links:
This guide will help you to add the widget to your form: How-to-Add-a-Widget-to-your-Form