@Tusoles It looks like the Pandora account connected to your Community profile is the one that is upgraded directly through Pandora (the one getting charged $5.66/month).
That would explain one of the charges.
If you are also getting charged for a subscription through Roku, then you might have a second account registered that is also upgraded via Roku.
This being said, you'll need to contact the Roku support team for further assistance with canceling and receiving a refund for any charges processed through their service. Otherwise, I'm afraid you'll continue to be billed each month. You can get in touch with them from the Roku Support page, or by phone at: (816) 272-8106. Hope this helps.
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