Make Phone Number Required During Registration

How can I make the phone number required for user registration?

In the admin panel…

Customers > Profile Fields

Under Contact Information, make Phone a Required field for Profile.

Also if you use PayPal express, then I found out they can still bypass the phone number requirement. On PayPal in the Profile I think under web payments you can require the phone #. Then their phone # will also be placed onto their order instead of the '0123456789'.

That is if you use PayPal express of course.