Glad to hear that US Cellular has good in-building coverage where you are. But if so, it is only because of the way they built out their network, carefully choosing antenna sites for good overlap between cells, and/or possibly offering to install in-building repeaters inside malls, large popular stores like WalMart, etc.

None of the wireless providers can get around the basic physics of radio-frequency electromagnetic waves and the attenuation of those waves, so the smart ones invest in their networks with plenty of cell sites, intelligently placed, then maintain them well. That's the ONLY magic to having a good wireless network, regardless of the signal frequency.