Delete an account after a change of name account and password

Hello. I want to delete the account from my iPhone but the problem is that the phone ask me my password.

BUT I already change the account name and password from another mac computer.

How can I do to give the password to my phone who ask the one from my old account name although I change the adresse name, so it doesnt find anything.

I hope I was clear, my english is not so good.

Thank you