Some of the extra money may have been applicable taxes.
Normally, all sales are considered final, but you can ask for a refund.
If you have received a confirmation email, click the Report a problem link at the bottom.
Purchases problem.
How long refunds from the App Store or other Apple services take.
If necessary, contact iTunes Support for assistance. See the Apple Support articles below for contact information.
iTunes Support – world wide
Apple Support schedule phone call
If necessary, try Twitter
https://twitter.com/AppleSupport. People have posted it may take an hour or more to get a response.