As an alternative, you can make a bank transfer on the bank account:
WIEN INTERNATIONAL
Verein für Bildung, Kultur in Soziales
VIENNA INTERNATIONAL
Association for Education, Culture and Social
Non-Profit Organization
Registered in Vienna (Austria)
Bank Account
BAWAG
IBAN: AT66 1400 0054 1012 2954
BIC: BAWAATWW
Please mention on your payment for which artist you are subscribing to.