If you want to force users to enter a telephone number in your contact us form here is a simple way to enable that.
Login to your admin and navigate to Appearance→Theme Options→Footer Block (within the options tab)
Note: If there is any content in your Footer Block be sure to leave it as is and add this to the bottom of that content (you don't want to loose what's already in there). Add the following javascript to the Footer Block and publish:
/* makes the phone field a required input in the contact us form */
<script>
$(document).ready(function () {
if ($('body').hasClass('ex-name-contactus')) {
// Get the tel input
var telInput = $("input[name=telephone]");
// Make it required
telInput.attr('required', true);
// Change label to Phone (removes - optional)
telInput.closest('.form-group').find('label').html('Phone');
}
});
</script>