How can I create a "confirm phone number" field like email?

I get phone numbers that are invalid since users are typing them quickly. I rely on these numbers for text responses. 

The email field has a useful option to re-enter email and make sure it matches. How do I do this for a phone number?

For that purpose, you could try using the "SMS Confirmation" to validate the phone numbers via your form: https://widgets.jotform.com/widget/sms_confirmation

Check this guide if you don't know how to add a widget to your form: https://www.jotform.com/help/252-How-to-Add-a-Widget-to-Your-Form 

Hope this helps. Let us know if you have more questions.