Thanks for posting. Could you please tell us what service you are pertaining to? Please take note that Chromecast is a plug and play device that doesn't come with a service. If the service you are pertaining to is for the app you used to cast videos to your TV, please reach out to the app developer to further assist you.
It looks like your concern is different from the original poster. With regards to a Google Account, you may post your concern in the Google Account Community forum. Also, you may check this support website article to see more information on how you can secure your account.