Switching between accounts in Alexa

My partner and I have two Alexa accounts, so we can each listen to our own Spotify playlists, etc. I am trying to send a command from HA to Alexa (via custom command to media_player.play_media service) to switch to a specific account, but it ignores the name of the account and just toggles to the other one.
Is there any way to tell which account Alexa is currently set to play from? Or a way to force it to either switch to the named account or else stay in that account if it’s already there?