If you want to get some peace and quiet then turning your phone off (or letting the battery run flat) is a good way to go. If you don’t want to do that then you could try the Blokket, a signal blocking phone pocket that is now available on Think Geek. The Blokket is made of a combination of silver and nylon and is said to block 99.7% of radio frequencies. Nobody has confirmed anything but I am going to go out on a limb and say that the other 0.3% more than likely belongs to the NSA, so there is no getting around that. It can also be used to secure your RFID chipped cards and passport – which is probably a good idea.
Anyway, it will stop the phone from getting signal, do you know what else it will do? Kill your battery – because your phone is going to suck up lots of juice while it attempts to find a signal. That makes your best course of action Airplane mode, or powering off… so if you win you lose and if you lose you lose, but that – unfortunately – is the way of all things.