The entire point of this is get referral contact info.
Asking for referral names / phone / email is the most important part!
The script below is for inspiration - please don't read it like a robot - add your own personality and choose your own words.
Small talk and chit chit help you both feel comfortable.
DO NOT CALL IT A SURVEY - IT MAKES PEOPLE FEEL WEIRD :-)
You're just calling to check in on them, and the questions will help guide the conversation.