It's not only a spanish problem, I have the same here in Germany. This evening I pay for my first on-month-subscription by paypal an 2 hours later I get the information, that I can use Spotfiy for the next 46 hours. Great !!! There are always a lot of possibilities to make money in the internet... ;-(
I would imagine that this was a simple billing error and not intentional. The best way to resolve this situation is to contact Spotify directly about the issue. They should be able to look up your account, and take whatever action is necessary to resolve the issue. You can find the contact form by clicking the "Contact" link in the "About Us" section at the bottom of the page. Once you get to the contact page, click the link labeled "Contact Form" and fill it out giving as much detail as possible. The more information you give them to help locate your account, the faster the issue can be resolved. Good luck getting your billing issues sorted!