In a regulatory filing, AT&T Inc. announced it will shut down its second-generation, or “2G,” wireless network by the end of 2016.

Twelve percent of the Dallas-based company’s contract-based plans, or 8.4 million people, have 2G phones and will need to upgrade to “3G” or “4G” handsets.

AT&T will shut down the 2G network city by city. Earlier this year it announced that the process had started in New York City.