This is a difficult situation. I guess DH will only look for the one who registered the account, and probably it is your agent.
Do you have the access to DH panel? Is the email address to log into DH panel yours?
If the email address is yours, you can renew your hosting plan via DH panel --> Billing --> Manage Accounts You can pay using credit card (if you have one by now luckily) or check). If the email address is not yours, it may be difficult for you. you should try to contact DH support via DH panel --> Support --> Contact Support or http://www.dreamhost.com/contact.cgi and explain your situation in detail. Then it will depend on your luck
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