Cancelled iTunes subscription

How did you cancel it exactly? What steps did you follow?

I would absolutely not cancel the card, or file a dispute as that generally just makes it harder to get things reslolved.

Start by verifying its actually cancelled by following the steps here: View, change, or cancel your subscriptions - Apple Support

Then contact iTunes Billing directly and see what they can do for you: iTunes Store - Contact Us - Apple Support

I would probably file a dispute with the card company. And contact Apple support and explain the situation. I hope you get the refund that you deserve. Good luck!