Hello Ruezoavau61
You can add the return ticket directly in the same purchase:
Or maybe you mean that you could get the return ticket but without the discount? Please note that there some limitations on the offer, as indicated on the Snow’n’Rail page:
If you need any help with your ticket and you want to ask for a refund, please check this page. You will also find the link to the refund form there.
I wish you a lovely day,
Chiara_S