What account are you referring to, and what are they doing? If you mean your Roku user account, they really can't do much with that. But you can go into your user account web page and change your password if you think someone else has gotten hold of it.
If you mean some other account (Netflix, Prime Video, Vudu, etc.) you would likely need to change your password with those providers as well.
Dan
Roku Community Streaming Expert
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