Help! Outlook Mobile

Help! Everytime I try to change my display name on outlook mobile (IOS) it doesn't work, it just simply goes back to displayingmy entire email address as my display name, the one the the recipient will see when i send them emails. How do I resolve this? I've already tried resetting the account, deleting it and uninstalling and reinstalling the app. Nothing seems to work! Any ideas of what else I could try?