Hello Chomboombau86
Please keep in mind, we are not the SBB Customer Service, I am not sure why you think we are. We are a travel support forum run by volunteering travel experts, we are helping people with our knowledge, we are not SBB employees.
It does not matter whether you have used or not the Swiss Half Fare Card, SBB cannot verify if you had used it or not.
You have to contact SBB using the contact form
https://sbb-tickets.cc/en/help-and-contact/customer-service/praise-comments/reklamation.html?stepId=3.17
Since it is time critical, you shall call SBB: +41 51 225 78 56.
You did a mistake, so there is at least little effort needed from your end in order to rectify the mistake. We cannot solve it for you but we can guide you.
Thanks for your understanding.
Kind regards,
Roland