It looks like there is a problem with your domain alexandralisboa.com.br. You can either have a .com domain or you can have a .br domain, but there is no domain that exists with the two combined.
I have refunded you the charge, and removed the Domain Mapping for this domain from your account so you can try again. You have two options:
1. You can attempt to purchase the domain alexandralisboa.com for your blog from the Store -> Domains page in your WordPress.com dashboard. This domain appears to be available at present.
2. You can purchase the domain alexandralisboa.br from a different registrar as WordPress.com only sells .com, .net, .org, and .me domains. After you purchase your .br domain elsewhere, you can map it to your WordPress.com blog by following the instructions at http://en.support.wordpress.com/domains/map-existing-domain/.
Let me know if you have any questions about any of the above.