Hi yangbai
The Schnupper Halbtax can be changed into a regular Half Fare Card provided it is renewed seamlessly. The already paid amount is taken into consideration at renewal.
Is the Schnupper Halbtax still valid now?
To renew it, see an SBB agent at the SBB travel centre or call the SBB Contact centre on 0848 44 66 88 (CHF 0.08/min.).
Best,
Roland