How do I opt out of Imzy sending me unsolicited messages asking me to post?

Two days ago, I recieved this message from imzy in the "chat with us" function:

Hi [name of former primary account]!

Everyone has more fun when there's lots of discussion. Will you make a comment today?

There was an option to thumb up or thumb down. I didn't see any option to unsubscribe. I thumbed down as the next best thing

Then today, I received this message in the same format:

Hi [name of former primary account]!

What's on your mind lately? Seen anything cool lately? You should make a post about it to Imzy!

It's not even like I never post or comment. I post nearly every day. I don't want to recieve messages like this ever, let alone once every two days.