Two factor authentication for no App users

[Ami]

Hello
Here is my test case: I have an app to manage a service. Part of that service includes people that don’t have my app but they rather call my help center. I need for a way to authenticate that they are who they say they are. So i thought of sending them a SMS message that includes a link. when they click the link i receive their phone number, if that phone number matches the one in the Database they are authenticated and i can provide them my service.

Is there a way someone knows?

Thanks