I've been a college student for about a year now and I'm still paying for the $9.99 subscription

Hi! I've been a college student for about a year now and I'm still paying for the $9.99 subscription. I clearly remember putting my student email and it's still charging me $9.99! Every time I go to change my subscription to the student one it always tells me that my student email is already in use. I need help figuring out why that is happening!

[Re-Titled by Moderator]