AT&T and Verizon are finally teaming up, and not for any project, but to develop VoLTE calling interoperability! The US carriers are working together to bring the voice over LTE feature work across carriers. This could possibly mean that soon™ you will be making calls from one carrier to another by using LTE rather than 3G technologies.
VoLTE is an all-IP technology meant to improve voice quality and add other services to the mix. VoLTE currently works within a carrier network which means, when you call to a number in another carrier, you will switch back to 3G networks, even if they are VoLTE capable.
Why would AT&T and Verizon work with one another? Because it may benefit them both on the long run. What would be the point of creating interoperable VoLTE calling if you can’t test it or use it with another carrier? This way they may get more customers and fewer complaints, along with better call service. The feature is expected to come live sometime in 2015.