Do you or have you ever had multiple Roku devices? If so, you may have multiple Roku devices. You can see the account that a device is linked to by checking the email address that's displayed under Settings->System->About on each device.
Can you access it using the stand-alone app or through The Roku Channel? It gets confusing with things that can be accessed in multiple mutually exclusive ways, but having access one way or the other would certainly show that you have an active subscription. For the stand-alone app, another way to manage the subscription is to highlight the Britbox icon on your Home Screen and press the * button on your remote. If you have a subscription through Roku there should be a "Manage subscription" option in the menu that pops up.
Beyond that, you'll probably only get the boilerplate here to contact billing/account support at https://support.roku.com/contactus .
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.
