add telephone number to email

[Guest]

My client has just asked for the customers telephone number to be included in the order email...

 

I know there's this code in catalog/order_process.php:

// send emails to other people
 if (SEND_EXTRA_ORDER_EMAILS_TO != '') {
   tep_mail('', SEND_EXTRA_ORDER_EMAILS_TO, EMAIL_TEXT_SUBJECT, nl2br($email_order), STORE_OWNER, STORE_OWNER_EMAIL_ADDRESS);
 }

 

but I don't understand it!! how can I add the telephone number to it?