the phone number field is set to use email validation
$WAFV_Errors .= WAValidateEM((isset($_POST["Phone_Number"])?$_POST["Phone_Number"]:"") . "",true,4);
open the server behaviors panel and click the server validation server behavior.
remove the email validation for the phone number field, then add it again using phone number validation.
you will also need to remove the validation show if for the phone number error, and add it again.