Change Username on Email

[onthehunt]

We recently changed email providers and I am tyring to update to the new info on my phone. I have the existing email account and only need to change the server info. Everything on the account is the same except the incoming and outgoing server info., which I can change. When it tries to setup, I get a message "incorrect username or password." That hasn't changed. I am not able to change the user name, it is grayed out. How can I change the user name without deleting the account and adding it again?