Q: Storage upgrade cancelled, but still being billed.

See ifiCloud storage upgrades and downgrades helps resolve this issue.

One week ahead of your billing period you get an e-mail from Apple letting you know the amount that is coming up. Did you get that e-mail? And did that charge show up on your card a week later? And then, how long ago did that charge show up on your card? And then, did you receive the e-mail from Apple saying that they had charged that amount?

If you have been billed and not refunded, according to http://support.apple.com/kb/HT4847 you can request a refund:

You can also cancel or downgrade your storage plan at any time. For a full refund, contact iCloud Support within 15 days of an upgrade or within 45 days after a yearly payment. Partial refunds are available where required by law.

Did you get the e-mail from Apple when they actually did the charge?

BUT ... are you actually being charged on your card? In other words, does it actually show up?