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.