iphone 5 memory full. need to restore firmware.
I have an original iPhone 5. The memory is always full even though I have very little on it. The settings say that Mail has 6.6 GB of data. That is not true and when I delete all the mail in the trash, sent, etc. , it doesn't change the 6.6 reading. Any ideas why this could be? Also, I cannot find how to restore firmware on the phone in iTunes. Thank you.
iPhone 5, iOS 7.0.4