Can I search and use previous order in the form as a starting point for the new order of the same customer?

I have built a pizza order form to test here in our location. These forms are strictly being used internally in place of orders being scribbled on paper, no payment processing at this point.

I believe that once orders are submitted, there is the ability to search for a previous order. The scenario I am looking at is, customer calls in pizza order, we fill out the form and submit. If that same customer calls again next week and we have his name or phone number we would search live in the submitted forms and open his previous order. I know I can edit that order but here is my question: Can I use that previous order as a starting point for the new order without overwriting the previously submitted order?

It's not possible. You can only search the submission via submissions page. If you edit the data, then that submission would be updated as well. Each submission has its own unique edit link. You need to load the form URL to enter a new data.

Let us know if you have any questions or if you need further assistance. 

Ok then if I search for previous order in submitted forms, open it, I can edit it and resubmit? 

Yes, you can do that. Please refer to the following guide to edit your form submissions in the form:

https://www.jotform.com/help/325-How-to-Edit-Submissions-Made-on-Your-Forms