If you think you have been hacked, then you should increase your security by changing your password and enabling two factor authentication and/or a pin for purchases.
If you are having account/subscription issues, then contact Roku customer support on their support page, go to contact, then accounts & subscriptions, select the issue and you should be able to chat or contact them by phone. You can also log into your account and see what subscriptions you have, if you purchased through Roku.
If there are other subscriptions, then you have to contact those channels customer support directly.
Finally, if you think your account was hacked and charges made, you need to contact your bank/credit card and report those charges.
If this channel is one for which you have a premium subscription through Roku, there will be a "Manage subscription" option instead of a "Remove channel" option. You can click this and follow the prompts to prevent further payments, but unless Roku changes its setup you will not be able to remove the channel through the Roku interface until the subscription expires.
While the subscription is in force you can use the official Roku remote app on an Android/iOS phone/tablet to remove the channel from your account.
At the bottom of the app's Home screen, click "Devices" and connect to one of them if not connected already. On the Devices page, click on "Apps on Roku" and find the channel you want to remove. Click AND HOLD on the channel to be presented with options to Launch the channel on your Roku, or to Remove the channel. (A quick click will instead bring up the remote control functions.)
Now Restart the Roku to remove all traces of this channel from the Roku's memory cache.
This will remove the channel from your Roku account and allow you to reinstall it, should you wish, in the hope of fixing your current problem, but it will NOT cancel the paid subscription to that channel if there is one.
