Create custom link url for users

I feel like this would be fairly simple to do?

You could generate a unique code to build your "referral link" for that user (e.g. http://www.mysite.com/refer/4Fg5GdXC45).

In the controller function "refer", you'd just look up which user that code belongs to, fetch their phone number, and pass that to the view. Or better yet, just send along the referrer user id and pull the phone number when processing the form submission. That way the user can't edit the locked fields using the console etc.