Buy a cell phone jammer if you want to project 30-foot cones of silenced phones. Or if you don't want to be arrested for using a jammer, build yourself a Faraday cage: no signal and no interference.

blocked call out

And here's a discussion of another kind of blocked call out.

I like the bit about worrying if criminals will jam cellphone signals (say while robbing banks). Surely, you'd want your criminals to announce their intentions that way. Seems like a cellphone provider could instantly detect widespread jamming and notify police right away.

Cellular providers do indeed monitor site traffic. Sudden loss of all calls for a given sector will generate an alarm. As of now equipment failure, rather than external jamming, is the first presumed cause.