NEW YORK (AP) — AT&T Inc. said Friday that the shutdown of its second-generation, or “2G,” wireless network will be complete by the end of 2016, a process that will force customers with older phones to upgrade to “3G” or “4G” handsets.

In a regulatory filing, the Dallas-based company said 12 percent of its customers on contract-based plans, or 8.4 million people, have 2G phones.