You are charged for the first attempt to reach an address. After an email hard bounces, you will no longer be charged since once it has bounced, the email address will not be sent to again.
If an email address hard bounces you are either on a block list somewhere or the email address simply no longer exists. Instead of making you go through all of your contacts and weed out the bad addresses, we simply eliminate them for you allowing you to free up valuable time.
At the present time, we would need to be contacted through support to add that person back in, since we would have to remove them from the universal blacklist here. This is another safety measure put in place to avoid clients being unfairly targeted by people looking to get money from them or resending after a client has opted not to receive their communications. Our support team will be happy to help in the event of a misunderstanding like this, however.