Do you talk to your students by telephone? Do you have a location in Canvas to maintain a record of the student's telephone number?
I believe it would be tedious if every instructor had to ask every student for their telephone number. We would need to have a field for a student to provide the contact information.
We have found you can add a telephone number in the "Add Login" portion of the student information page. Instead of a login name, enter a contact number. No password should be entered. All instructors have access and other students will not see it. This capability to add this is only available to Account Admins.