im pretty sure that when i joined in Jan-2007 a creditcard was the only way to get premium ?
*sidenote i also changed the payment method to paypal (*early last year i think)
judging by the last post things might have changed ?
but i used the "wirecard" which is a virtual mastercard and works like a debit-card, they also have a "wirecard" island in sl where you could go for some quick support or questions