Apologies for the late reply, but maybe I can still help :)
Most of the times a user gets charged after he cancelled, is because he never ended the cancelling process. There are two ways to check this. First, you can see this on your subscriptions page. And Second, you can check your email for a confirmation of the cancellation process. When these methods say that you are still on Premium, please try to cancel again, this time being aware of receiving the cancellation email. The process asks a few times if "you’re really sure" you’d like to cancel, and if not careful, it's easy to oversee them.
Have a nice day!
LukeRock Star 17
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