The AT&T Microcell was a "femtocell" device manufactured by Cisco and sold by AT&T between 2009 and 2017.
MIcrocells utilized a home's broadband Internet connection to create a small 3G cellular network, allowing users to make calls even if cell service was previously weak. Essentially the unit operated like a "mini cell tower" in your home.
AT&T discontinued the MicroCell in 2017, but existing devices will continue to work until AT&T's 3G network is shut down in February 2022.
Verizon sells a device called a Network Extender. It uses a home internet connection to create an "LTE network" at your home. For most users, a Network Extender isn't a great choice: many people don't have reliable enough broadband at home to begin with, which is part of the reason they're boosting their cell signal.