i believe car radios are banned on petrol forecourts since they instruct one to switch off engine and ignition.
When you consider that mobiles have batteries in side them and that many people wear them on their belts, just think how close they come to the nozzle of the fuel pump during refueling and how much vapour escapes out of the filler pipe, particularly on a hot day. .. a knackered old phone, a call coming in just as you spill some petrol.
In oz they have had cases of explosions due to mobiles ccording to local papers.