AT&T will begin offering new roaming deals for customers who use their phones in Mexico and Canada. Starting May 20, AT&T Unlimited Plan members will not incur any roaming charges in those two countries.

AT&T

AT&T says:

AT&T Unlimited Plan customers will need to separately add the AT&T Roam North America feature to each smartphone and the Roam North America Data feature to each tablet, both at no additional charge, to activate the roaming benefits. The features can be added through myAT&T, online at http://www.att.com, or by calling AT&T.

In addition, customers on the carrier's Mobile Share Value plans for 15GB of monthly data and higher will also get free roaming in Mexico for no additional charge,