Among the wireless communications service providers in the United States, Verizon will no longer allow phones that don't support VoLTE, a standard high-speed wireless communication for mobile phones.
In 2019, Verizon announced that they plan to shut down their CDMA2000 network by the end of 2020, making VoLTE the only way to make calls on their network. Voice over Long-Term Evolution (VoLTE) is a standard high-speed wireless communication for mobile phones and data terminals, including Internet of things (IoT) devices and wearables. 
