Very similar thing happened to me last year. I have an MLB.TV subscription and was trying to watch it on the weekend when visiting my parents while using their Roku. I thought I had logged in under my credentials on their Roku so I could watch and they ended up getting billed by Roku for an MLB subscription. Never did get it straightened out.
We understand that you are inquiring about a charge through your Roku Pay, is that correct?
For these inquiries related to Roku Pay, it may be more effective for you to get help from our billing team. Please contact them directly through our Account-Billing Support page. Choose the options for "Account, payments & subscriptions" and they are the best ones to help you out with that matter.
If you have any other questions or concerns, please let us know.