For these issues, it may be more effective for you to get help from our billing team. Please contact them directly at https://support.roku.com/contactus. Choose the option from the drop-down menu for "Questions about my account or billing," and you'll be able to send an email request there.
Any subscriptions you've obtained through other services (Hulu, Prime Video, etc.) will have to be unsubscribed through those services.
Any subscriptions obtained directly from the channel will have to be unsubscribed on the channel's website.
Note that most (all?) subscriptions pre-pay (or provide a temporary free trial) for a defined subscription period and auto-renew when the subscription period expires. When you unsubscribe it stops the auto-renewal but the current subscription stays active until the current subscription period runs out. Few, if any, will cancel immediately and refund the unused portion of your prepaid subscription. This is all explained in the conditions you agree to when you subscribe (you know, all that stuff we all agree to without actually reading it).
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T