Whispernet service is now available in Spain. Kindle (U.S. & International Wireless) customers from the United States can travel internationally and still get books in less than 60 seconds. Customers have the option to wirelessly download books, periodicals and personal documents via Whispernet for a fee or transfer files from their computer for free.
* International Book Service: Download books from your Kindle's Archived Items or the Kindle store via Whispernet for $1.99 per book.
* International Subscription Service: Receive all of your newspaper, magazine, and blog subscription content via Whispernet for a weekly fee of $4.99.
* International Current Issue Service: Download individual issues of newspapers and magazines from your Kindle's Archived Items or the Kindle store via Whispernet for $1.99 per issue.
* International Personal Document Service: Transfer personal documents to your Kindle via Whispernet for $.99 per megabyte (rounded up to the next whole megabyte). For more information about transferring personal files to your Kindle, see the Transferring, Downloading, and Sending Files to Kindle Help page.
I'm sorry as currently we don't provide any upgradation to US units to international ones.
Hope this helps! Thank you for your interest in Kindle.