It is doubtful you can. Contact Charter to see what provisions they have. In the meantime, I suggest getting a gmail email account, or something similar. That will give you an email address that you can use regarless of who your ISP is. As soon as you establish a "permaent" email address, go to your account in Charter and set up an autoforward and an autoreply. The autoforward to send all of your mail to your new address and a reply to all your senders giving them your new email address.
You should also capture your address book from charter's web mail system and transfer them to your new mail service.