Michael Flatt wrote: The Laws of Chess apply in full.
As always with rules drafted and redrafted by committees, there are anomalies.
If you don't read 11 b, or regard it as set aside in part by the "in a bag" interpretation, there's also 12.8 and 12.9
12.8
Unless authorised by the arbiter, it is forbidden for anybody to use a mobile phone or any kind of communication device in the playing venue or any contiguous area designated by the arbiter.
12.9
Options available to the arbiter concerning penalties:
a.warning
b.increasing the remaining time of the opponent
c.reducing the remaining time of the offending player
d.increasing the points scored in the game by the opponent to the maximum available for that game
e.reducing the points scored in the game by the offending person
f.declaring the game to be lost by the offending player (the arbiter shall also decide the opponent’s score)
g.a fine announced in advance
h.expulsion from the competition.
Provided you interpret a phone ringing or otherwise making a noise as "use", then awarding the game to the opponent is the application of penalty f. Lesser penalties such as a warning are also available.
British tournament arbiters for the most part have continued with the now traditional warning that mobile phones should be switched and you lose if they make a noise. Some have gone on to make the point that the phone should be out of use and seen to be out of use for the whole game, meaning that you leave the phone behind if you leave the room.