Hello Vowixain39
Of course, you do have the option to select the first day of validity; if you do not change it upon purchase, the system assumes you want to use it instantly.
If you bought the Swiss Travel Pass from the SBB website (sbb.ch), please asap call the SBB Contact Center: +41 51 225 78 56 (24/7, waiting times may occur). Otherwise, you have to get in touch with the agency from where you purchase the Swiss Travel Pass.
Usually, you cannot refund the passes retroactively, as there is no proof of non-use. Hence, call SBB as soon as practical.
Kind regards,
Roland