Potentially being scammed

[nyzccccc]

Hi!
I recently purchased an game account off of a guy who was using this roundcube domain? or whatever. I am not familiar with this type of stuff and I am here to ask help with my email.
So after buying the game account I recieved the login information and the email was created using roundcube. Right after recieveing the login info, I logged on and tried to change the password, but couldn't. After looking around the mail website I saw that this email platform allows you to install add-ons and such. The seller has installed an add-on named "password" and I suspect that this add-on doesn't let me change the password of the mail.
Any suggestions on how to remove this so I could change my password will be appreciated. Also if I can't do anything about it, please let me know ASAP.
Thanks!

[JohnDoh]

There is no such thing as a "roundcube domain". Roundcube is a web based IMAP client. For things like changing passwords or confirming the ownership of the account you need to contact the email provider.

The password plugin that ships with Roundcube allows an account's password to be changed via the interface but it has to be configured to interact with the IMAP server to do this.