Send payment information by email to the customer

-- url of the page with the problem -- : www.portal-gestao.com
-- HikaShop version -- : 240
-- Joomla version -- : 341
-- Browser(s) name and version -- : Chrome

Hello,

I've created a custom payment method by hacking the core Western Union's.

On the last page, after the order is complete teh customer gets a reference for payment ("Multibanco" here in Portugal).

He sees something like this:

Entity: 123123
Reference: 12312313
Value: € 12,12

It is working OK, the PHP function to generate this reference was added to western_union_end.php

But how do I include the reference also in the email sent to the customer, like it happens with the bank transfer account information?

Thank you for your support!