After getting approved, you should have gotten an email with steps on how to unlock the device. Should resemble the steps on our Mobile Device Unlock: Apple iPhone on iOS 11 page. Have you checked your spam and junk folders to see if that email confirmation is there?
Good morning, magenta6726390!
Just swinging by to see if you've received the confirmation email to unlock your iPhone. If not, please take a look at MC's post above and follow those steps to unlock your phone. If you're still having issues please let us know so we can try some additional troubleshooting with you.