First I opened a ticket at SE Support Center ("Contact Us"). Category: Billing/Payment and subject "Error 401/ 601". You have to send them the following information (explained here:
http://support.eu.square-enix.com/fa...=2&kid=68643):
o SQEXID
o Payment method you are trying to use (credit/debit card or Crysta)
o Type of the card used (Visa, MasterCard, etc.)
o Country the card was issued in
o Country you are currently in
o Name of the bank that issued the card
o Number of times you tried to process the payment after you got the initial error message
After filling out all the gaps you receive a confirmation email. A few days later they contacted me via email and asked for the picture of the credit card. So I sent the picture as requested (only last 4 numbers visible) to
sel-id@square-enix.com. Subject was my ticket number. In the body of the email I just wrote "... picture of my credit card as requsted", my SquareEnix ID and the ticket number again.
I had to be patient, but they solved the problem. :-)