Q: cancel my monthly storage charge now!

The only problem is this is not the correct place to ask so that is not going to help in the least getting your iCould canceled.

Try Manage your iCloud storage - Apple Support

You are not talking to Apple. This is a user to user forum.

Asking on a forum to cancel charging does nothing really.

And since you agreed to be charged, until such time as you physically cancel your subscription, it is not illegal for Apple to charge you.

You can downgrade your storage plan. It will take effect the next time it is up for renewal.

iCloud storage upgrades and downgrades - Apple Support