How do I change the sender name (display) on my email account

Go to Settings>Accounts & Passwords>select the account in question, then tap on the account page, and you should see the Account Information, including Name, Email, Description. Change the name there.

Have you tried selecting your card in Contacts, then Contacts/Card/Make This My Card?

see this http://www.idownloadblog.com/2015/06/02/how-to-change-email-display-name/