Huh?
AT&T has implemented RCS;
"
Yes! The Advanced Messaging enhancements being introduced to Android smartphones adhere to RCS standards. AT&T has made a number of network updates to support Advanced Messaging. We continue to bring RCS to devices within our network, and provide RCS interconnectivity between major mobile carriers."
Advanced messaging lets you share your life like never before with higher quality photos & longer videos. Find phones that support advanced messaging at AT&T.
www.att.com
Have to check on TMo but my Android is on TMo and I use RCS via Google Messages.
Learn about T-Mobile and Google's partnership to enable T-Mobile customers with Rich Communication Services while texting Android users on other networks.
www.t-mobile.com