change my user name in Outllook.comaccount

In outlook.com, my primary alias setup shows that my 'user name' is actually my email address. I think this is causing some problems (Outlook.com says it is having trouble getting this mail). This is also the name which shows under my actual name which is on my computer sign-in page. Would really like to change it but it does not allow. My windows phone (if that's where it came from - but I don't think so - is temporarily on the shelf while I deal with this account. Using my old phone. Can't change back without going to store and getting a new SIM card.