There are fairly regular posts on here about phishing emails saying that something has been purchased on their account, quite often with 'click her to request a refund' in them. These will hopefully help to check if it's genuine or not (generally real emails will be personalised, not 'dear customer', 'hello' etc, and be written in proper grammatical language) :
Phishing and similar emails : Phishing & Other Suspicious Emails
Phishing emails : Identifying fraudulent "phishing" email - Apple Support
Genuine iTunes emails : Identifying legitimate emails from the iTunes Store - Apple Support
Viewing your account's purchase history : See your purchase history in the iTunes Store - Apple Support (on an iOS device you can view the last 90 days purchases via http://reportaproblem.apple.com)
If it is a phishing email you could forward it to Apple : reportphishing@apple.com , and then delete it.