The following post shows how to ask a customer to leave their phone number during the feedback process. This is great option if you don't already have your customers phone number and if you want to follow up in person via phone to positive or negative reviews.
1) Log into your GatherUp.com account
2) Click on the Business you would like to activate the Phone Number entry field for.
3) In the main menu (upper right) click on "Settings -> Feedback Settings" and check the phone option box.
To retrieve a phone number, search for the customer in your Customer Dashboard and click on the customer name to enter the Customer Details screen.