Call the Lagos embassy at this number: 012278955, they're the ones that handle the CGI website, you'll be put on hold or the number might not connect for a while, but keep trying, once you're connected with an agent, explain it to them in detail, you'll be told to provide a new/unique email so that they can transfer your former email to the new one, you'll also be told to provide a scanned copy of your passport. After a day, you should receive an email confirming your new email and a temporary password, if you don't get the email after a day, call them again and have them do it over the phone while you're on the line with them.

Greatajo:
EVENING HOUSE, I APPLIED FOR A VISA EARLY LAST YEAR BUT WASNT GRANTED. NOW, I GOT ADMISSION TO ANOTHER SCHOOL AND WANT TO APPLY AGAIN BUT WITH A DIFFERENT EMAIL. WHILE FILLING OUT THE VISA APPOINTMENT FORM, I GOT A RESPONSE THAT MY DETAILS MATCHES ONE ON THE DATABASE WHICH HAPPENS TO BE THE EMAIL I USED LAST YEAR. MY PROBLEM NOW IS THAT I NO LONGER HAVE ACCESS TO THAT EMAIL AND ALSO, THIS NEW EMAIL WAS THE ONE I USED FOR VISA APPLICATION BUT THEY WANT TO TRANSFER MY DETAILS TO THE PREVIOUS ONE. HOW DO I GO ABOUT IT PLEASE