You cannot select the seat by the number online on our website. You’ll get a seat that’s free, respecting the selected desire of location.
Anyways, it’s possible to check on the SBB railcounter at the train station if a seat nearby is free. Or you can simply call the SBB Contact Center +41 848 44 66 88 (CHF 0.08/Min.) or from abroad +41 51 225 78 00.
Thank you for your understanding and have a nice day.
Kind regards, VlaznimA.