Using the email address shown via Roku path Settings > System > About, log into your account at https://my.roku.com. Once there, check your Roku purchase history. If you have multiple Rokus, check Settings > System > About on all of them and if you have other email addresses shown, check those Roku accounts too.
Keep in mind that scammers can call their bogus charges anything they like. Don't assume that a charge that says it's from Roku necessarily is from Roku -- ESPECIALLY if the charge does not show up when you when you check your account at Roku.com.
Challenge any remaining unidentified charges with the financial institution through which these charges are arriving. They can trace the charges back to their actual source.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X