Cancelling iTunes Match

That should work. The site Subscribe to iTunes Match - Apple Support

shows the same thing:

Cancel your iTunes Match subscription

By default, your iTunes Match subscription automatically renews at the end of your one-year subscription. Learn how to cancel your subscription.

The only possibility I can think of is if you have more than one Apple ID and it is under another one. If that doesn't help, contact iTunes Support. You can do that by using the link below from If you see apple.com/bill, itunes.com/bill, or an unfamiliar charge on your statement - Apple Support

If you followed the steps above and you didn't find out why you were charged, contact Apple Support.

See: View, change, or cancel your subscriptions - Apple Support