Freeform block unsubscribes user if already in list

This may be one of those dim moments on my behalf, but I cannot figure this out.

I have dont the following:
Setup the mailchimp module and import lists
Allow anonymous registrations
All settings checkboxes are empty
Add the mailchimp subscription block to my site

When a user types in their name & email and submit, they are usually correctly added to the list, and a message appears saying "You have subscribed to [list]"

HOWEVER, if a user is already in the list, submitting their name & email causes them to be removed from the list, and a message appears saying "You have unsubscribed from [list]".

I've tried this multiple times, submitting the same email address again and again. Each time it toggles between "subscribed" and "unsubscribed". I confirm this on the mailchimp end of things, the user is removed and added repeatedly.

Is this behavior expected? How do I prevent it? I am afraid people may forget if they are already signed up, and submit their email on the site, and then not notice the relatively inconspicuous message that says "you have UNsubscribed", and leave happy that they are on when in fact they just got removed.

Ideally, the freeform block would only subscribe - if an address is submitted that is already in the mailchimp lis, it should either do nothing, post a message to the essence of "you are already registered", or update the entry.

Thank you for your support.