I have to do the same thing because I wanted to get verified so I double checked my information first and saw that for some reason my year of birth is one digit off for some reason. I looked into how I can fix it and read that you have to submit a ticket. You can do it right on the app. Good luck and let me know if they fix it for you!
Tara is right - in order to get your Date Of Birth (or name, or gender) updated, you should upload a photo of your valid, undoctored, government-issued ID on your Extended Profile on iSecretShop, and then open a support ticket to let the iSS team know, and your DOB will be updated.
Previously, shoppers could change their DOB, name and gender at will, along with any other information, and this created security issues - fraudulent shoppers would take advantage of this, changing their profile information (name, gender, birthday, address, email, etc) often, in order to avoid being detected by the system for having multiple profiles or profiles with false info.
Since the general idea/rule is that all shoppers can only have one profile on iSecretShop, and that one profile should reflect their real information, this method helps maintain the system integrity, making it more secure and less prone to exploitation by people who are looking to "bend the rules".