Hello yh2911
In the case of the GA monthly travel pass, you cannot terminate ongoing contractual travel passes such as the Half-Fare travel pass early, nor can you have them refunded, as the GA monthly travel pass is not contractual and the term of the travel pass ends after one month.
For more information about subscriptions, I recommend you to contact our customer service on +41848 44 66 88 (CHF0.08/min).
I wish you all the best.
Greetings
DafineM