Pretty sure I just figured out how to stop this! I agree it's super annoying. You can change the default app that alexa uses to respond to artist name or genre requests. Deselect pandora as an option and then you have to tell her to play a station "on pandora" otherwise she'll use Amazon music. Huzzah! See attached app screen shots. Get to this screen and click change to deselect Pandora.   ... View more