However, you still need to have an AT&T post paid account to access WiFi-C on AT&T's network and your service area needs to be provisioned for VoLTE (HD Voice). It uses your WiFi connection to reach the AT&T Mobility servers.

What AT&T and us recommend now is WiFi-C (WiFi Calling) if your phone is capable.

You also need to live in a MicroCell Service Area, which in most cases, is the same as the AT&T Cellular Service Area. You need to have a land-based internet service (cable, DSL, or fiber), a post paid AT&T cellular account, and ideally not live in a rural area because of the FCC E911 requirements ( your GPS coordinates must match the physical address of your house). It uses your internet connection to reach the AT&T Mobility servers. You can find used ones on eBay but there are caveats to that (see my Tech Guide for info on purchasing second-hand MicroCell, link is in my sig line). AT&T will continue to support it through this year but the service itself will eventually be discontinued. Sales of the MicroCell were discontinued at the end of 2017 because the MicroCell has reached its EOL.

At&t cell phone booster