GAWD....I know how you feel. When I first worked for British Airways...I sent someone to the right city name...but wrong country. Hopefully, they caught it before they took off....but airline tickets can be hard to read and it was a last minute emergency/death thing. I couldn't reach the person the next day after I realized my mistake. I tried calling the aiport involved...but h*ll, it was in the country of Georgia and I couldn't speak the language to the person on the other end of the phone. It's haunted me for years.
I don't know what to tell you. Admit openly that you made a mistake and take what comes with it. If you don't screw up often...maybe it'll be okay...other than a pissed off client. I'm not sure if it's a basis on which your employer could fire you for since I don't know much about your business.
It's now Monday.....what happened?