It sounds like you probably called a scammer to set up your Roku. You should set up a Roku directly following the instructions on the screen exactly. If during setup, you call someone on a phone, then it's about 99.99% certain that you're being scammed.
If you like, you can set up your Roku account here without even using a credit card:
https://my.roku.com/signup/nocc
That way Roku won't be able to charge you for anything.