The new plan will allow users to make calls while browse the Internet at the same time, which is currently still quite problematic.
It will also be possible to make a call and continue browsing the net without interruption of any kind.
AT&T said that the Samsung Galaxy S4 mini will be the first mobile device to use the service.
Apple announced the iPhone 5 will support HD audio calls on some operator networks. Although the iPhone chip supports calls over LTE, it is currently not supported on iOS.
However, it is expected the iPhone 6 that will be released this fall and the iOS 8 will complement each other to support VoLTE calls.
This project will be tested in the states of Illinois, Indiana, Minnesota and Wisconsin, starting May 23rd.
Besides AT&T, Japan’s major carier NTT DoCoMo has announced the implementation of VoLTE support in June.