I've used Nokias (5190, 6160, 6190, and 8290). None of them worked in my office building, but no one else's does either. Before you get a new phone (unless you're looking for an excuse to upgrade), make sure that 1. another carrier doesn't get signal, 2. a different type of cell phone on the same carrier doesn't get signal, and 3. you actually get strong signal outside your building.
gm