You should be able to cancel any subscriptions you obtained via Roku via your account at my.roku.com. Any subscriptions obtained directly with the channel will have to be canceled directly with the channel. You should be able to tell which is which by seeing who is charging your credit card for each subscription.
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi LivRm - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi BedRm - JVC EM37T
Roku 3, 4200X, Ser 4124C7087583, wifi GstRm - Sanyo DP26640