I would call the booking agent again and tell them you want them to correct the mistake. If they say no, tell them that you will not only write a review of their company and blast it all over the internet but that you will take up a dispute with your credit card. When you call, insist that you speak to a manager right off the bat. I can't imagine that people do not make mistakes entering dates all the time. Maybe they will issue a credit, even though you might have to go back to finding a hotel on your own at the last minute.
In the end, if you're not able to make any headway with the agent, just remember that you'll be on vacay with your BF and you'll have a great time. You'll barely be in your room anyway. Since your room is now at issue, I have to mention that you should check the places you stay for bedbugs. You do not want to bring those things home!
Worried about bed bugs in your hotel room? - Travel - Travel Tips - msnbc.com