Apple has actually included an assistance document to its web site specifying that customers that make use of an AOL username to authorize right into the iTunes Store- https://ituneshelp.org/itunes-account-login/
Apple customers need to transform their AOL username to an Apple ID account in order to preserve access to the stores adhering to the target date- http://www.bricksite.com/ituneshelptop
Starting March 31, 2015, AOL will certainly not enable customers to use their AOL Username to check in to the iTunes Store, App Store, or iBooks Store- http://ituneshelptype.greatwebsitebuilder.com/
You must convert your AOL Username to an Apple ID in order to maintain access to the stores and to content you bought previously.