Today is the final day for users of AT&T cellular service to switch over to phones that can manage 4G or 5G services.

The company is shutting down it’s 3G services, meaning numerous older style phones will simply quit working.

That includes old flip phones and old devices that haven’t or can’t been upgraded, but it also includes fire and intrusion systems, home health care devices, such as life alerts, and some GPS tracking devices connected to cell service.

AT&T is making the switch today, while T-Mobile will make the change in July and Verizon will go in December.