PowerApps- Field Validation in the submit form function. phone and Email

For the Icon or button you use for a form submit.  Place formula in the "OnSelect" property.
(Tests for "true", a true result: submit the form, false result: it displays an error message on top of the page.)

           And (IsMatch(DataCardValue7_1.Text, 
            Digit & Digit & Digit & Hyphen & Digit & Digit& Digit& Hyphen & Digit & Digit & Digit &Digit)),
   Notify("Fields not valid on this page, please check", NotificationType.Error)