Maestro, using American terminology, is the debit card counterpart of Mastercard.
You should *never* use a debit card to sign up for internet services - unlike credit cards, there is no protection in case of fraud, and no legal obligation on the banks to allow you to dispute the charge. With a credit card, if a service doesn't allow you to quit, you have recourse and will probably be refunded any money you pay for a service you don't use. No such luck with a debit card.