How do I get my money back from a purchase I didn’t make

Where are you seeing the purchase ? If it shows on your iTunes account's purchase history, and if you claim you didn't do it, contact iTunes Support : http://www.apple.com/support/itunes/ww (click on your country's flag, the country where you live, and which is therefore the country on the account ; click on Contact Support towards the top right ; click on Get Help under 'Talk To Us’)

Does it still show as cancelled ? And when was the charge ? If you cancelled it less than 24 hours prior to its renewal date it would likely still renew for another term.