Starting in February, U.S. cellular carriers will begin to shut down 3G. WSJ’s Joanna Stern got an old iPhone 3G and iPhone 4 working on the old network, in order to remember all it did to shape the smartphone revolution. Photo illustration: Preston Jessee for The Wall Street Journal More from the Wall Street Journal: Visit WSJ.com: http://www.wsj.com/ Visit the WSJ Video Center: https://wsj.com/video On Facebook: https://www.facebook.com/pg/wsj/videos/ On Twitter: https://twitter.com/WSJ On Snapchat: https://on.wsj.com/2ratjSM #3G #iPhone #JoannaStern