While it is probably good practice not to use your mobile at gas stations, it is commonly accepted that the risk of a mobile being the source of ignition is very small and in most cases the presence of a mobile phone at an explosion is merely coincidental. Static electricity is often the actual source of ignition, among other things.

There's more info here.

That said, I can't believe anyone has business that is so important that making or answering a call can't wait until they've left the petrol station, so it's probably better to be safe than sorry. And of course, if there's a sign saying "switch off your mobile" it is only polite to oblige (though this is unlikely in Qatar if the ignorance of "no smoking" signs in cafes/restaurants is anything to go by).

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