Had the exact same thing happen. Only we used a company vetted/recommended by AWS to set this up for us, as we have no AWS experts and we're all too busy tasked doing actual startup things. So we staffed it out. Even the "professionals" get it wrong, and we racked up a huge expense as well. Staffed out company shrugged shoulders, and then just said sorry about your tab. We worked with AWS support to correct situation, and cried to daddy AWS account manager for a negotiated rate.