No. We won't charge you without warning or telling you first. We merely need your credit card to avoid spammers and certain younger people trying out the service without knowing what it really does. We want to focus all of our time on professionals, or professional individuals.
Once your account exceeds 100 followers, we will send you a notification and you have to upgrade manually, eventually, we won't do this for you. So there will be no charges until you upgrade yourself later down the road.