Hello hyun
Welcome to the SBB Community.
I don’t have a half-fair card, but if I buy another Saber Day Pass with a half-fair discount, is there any problem traveling?
This is not recommended. Instead, you could purchase another full fare Saver Day Pass and then contact SBB to refund the wrong one (name, date of birth, travel date must be identical):
+41 51 225 78 56 (24/7, waiting times are possible)
Are you sure, the Swiss Half Fare Card would not be beneficial?
Kind regards,
Roland