Hello jstucki
Thank you for your question.
If our regular number (0041 848 44 66 88, CHF 0.08/min) does not work, please try 0041 51 225 78 00.
You can also try to split the journey while doing the online purchase: the first section Zermatt > Geneva (or the departure train station) and then Geneva > Paris.
I wish you a great day.
Kind regards,
FatimaH