So i have tried to get the ".yml" files to work, without any luck what so ever!

Because we are a pizza shop with deliveries, i would very much like to add in some way for the delivery boys and girls to be able to call up the customers when they are not around when they are there. Which files should i edit? And what should i edit? Exactly? I have tried the order_invoice.twig and also the order.php files in controller. After editing any of them, nothing happens

Ideas? Really need this done as soon as possible

Any help, thanks in advance!
