AT&T plans to permanently shut down all 3G services as they say they are making room for their new 5G services.
Starting Tuesday, all devices using the 3G service will no longer work.
The changes could impact millions, according to AP.
Many older flip phones, medical alert devices and home alarm systems still rely on the 3G services and will no longer work come Tuesday. According to AP, 1.5 million families still have a 3G home alarm system that needs to be upgraded.
For some, it's the cost of a new phone that's keeping them from upgrading. But Dimity Orlet, an advocate at ProSeniors, says that's not the case for everyone, specifically those using the 3G service for their medical devices.
"We need to get the word out to Seniors, but also folks, family members, and friends to make sure their devices are going to work with the new 5G," Orlet said.
An AT&T spokesperson tells NBC it is "helping customers navigate this transition" and "will provide free replacement phones" to majority of people using older flip phones.