I booked a semi-flex Lyria ticket from Geneva to Paris. I now want to exchange it for either a later train or a route from Lausanne to Paris. I have to do it 7 days in advance at a ticket office, but I won’t be in Switzerland seven days in advance of the train to do so. I thought I would be able to make a change on the excellent SBB app. Calling from overseas, sounds difficult and expensive. Any other options? Thanks