The story
Prior to brand standardization by SBC Communications, Ameritech directories were published under the PagesPlus brand. Ameritech Publishing's operations in Illinois and northwest Indiana were placed in a partnership with R. H. Donnelley, called DonTech, in 1999. Following brand standardization since 2002, Ameritech Publishing, the company, is currently known as Ameritech Publishing, Inc. d/b/a AT&T Advertising & Publishing.
From Wikipedia’s article on Ameritech Publishing, shared under CC BY-SA 4.0.3