Check on your Roku account and see if you have any subscriptions listed that may have been accidentally purchased.
You can also reach out to Roku customer support on their support page. On that page, go to contact, accounts/payments and then click on the next page, and then you should be able to chat/talk with CS. I believe that they are available until 10 PM EST.
If you have an unauthorized charge, I suggest contacting your bank/credit card and letting them know as someone may have hacked your credit card.