Hello Quaiweevee65
Again, we are a travel support forum run by volunteer travel experts, we are not the SBB Customer Service.
International tickets, if possible at all, can be cancelled by phone or in person at the station, only.
The number you have mentioned does not work from all countries.
It is advisable to book the tickets from an operating company, not a third party company like SBB.
I cannot help more than refer to the phole number I mentioned above.
Kind regards,
Roland