For us we use ZoiPer and the click to dial function would take the number as shown in OSTicket 5555555555 X133 and hyperlink it to 5555555555133 instead of putting a , between or only looking at the number. So i edited class.forms.php to display at + instead of an X. The number and the extension are both in a single column in the DB fyi

File to edit

include/class.forms.php

change
$phone.=" x$ext";
to
$phone.=" +$ext";

----------------original--------------

}

function toString($value) {
    $config = $this->getConfiguration();
    list($phone, $ext) = explode("X", $value, 2);
    switch ($config['format']) {
    case 'us':
        $phone = Format::phone($phone);
        break;
    }
    if ($ext)
        $phone.=" x$ext";
    return $phone;
}