How to prevent user to input fake number?

People input fake numbers. How do you avoid this? It's a problem.

Hello Albert,

Thanks for reaching out to Jotform Support. I would suggest using the SMS confirmation to verify that the number inputted is active. With this, when a user provides their phone number, they’ll receive a verification code they can use to continue filling out your form.

GIve it a try and let us know if you need any other help.