First, the phone app does not allow you to watch what's on the Roku. Other than The Roku Channel, you can't watch anything that's on the Roku. Depending on the provider, you might be able to watch their content on your phone, but that would have nothing to do with the Roku.
Next, I don't think you downloaded the official Roku app. I've never seen anything in the Roku app that requires a payment or subscription.
Dan
Roku Community Streaming Expert
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