I don't see the point of trying to withdraw your application; who knows how long that would take.
I would send them an e-mail and a letter, explaining that you made a mistake filling out the form and wish to correct it. Include your date of birth and Client ID (from your work permit). Maybe even fill out the form again, without the mistake, and include that. That makes it easy for them to be reasonable; all they have to do is throw away the old form and put the new one in your file.