If you're Roku account doesn't show any subscriptions at https://my.roku.com/account/subscriptions then you're probably right - your credit card has been compromised. Roku won't be any help getting to the bottom of it. You're better off going to your credit card company and getting them to get to the bottom of it. The only "official" answer you'll get here is, "for account or billing issues go to https://support.roku.com/contactus ". From experience, if your account doesn't show any subscriptions they will just wash their hands of the whole situation.
I don't know if this applies, but if you have multiple Roku devices then more than one person has unwittingly created more than one Roku account. You can check what account a Roku device is linked to by checking the email address displayed under Settings->System->About.
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