I've seen companies say things like:
"Provide Cellular Coverage using Wi-Fi"
or
"Improve and control Cell Phone Coverage in All Your Facilities..."
or
"A feature that allows cellular devices to use your Wi-Fi network as if it were a cell tower"
Just to point out, any Wi-Fi system can NOT, and does NOT, provide cellular coverage to any cellular radio. Wi-Fi can ONLY provide Wi-Fi coverage to Wi-Fi radios.
That said, there ARE solutions using Hotspot 2.0/PassPoint or OpenRoaming that can provide Fast, Free, Frictionless and SECURE Wi-Fi connectivity to Wi-Fi client devices.