In general, it's possible to subscribe to a service in two ways - through Roku or directly through the provider. Roku has no way to know if you subscribed directly through the provider and often the provider has no way to know you subscribed through Roku. If you had a Roku subscription and you cancelled (verify at https://my.roku.com/account/subscriptions ) then they shouldn't have billed you. "Roku" will appear in the description on your statement if they billed you. If Philo billed you then Roku is completely out of the loop.
I know subscriptions are confusing and Roku certainly shares the blame. If you had two subscriptions to the same service you wouldn't be the first person.
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