Mobile phones and in-vehicle Multi-media Devices
You must not hold any communication device while driving. That covers a phone in your hand, a hand-held microphone, and anything else you have to hold, look at or work while the vehicle is moving. Proper control of the vehicle is the driver's first duty, and one hand on the wheel is not proper control.
Very few people can successfully do two things at the same time, and no one can use the road safely unless their attention is fully directed towards doing so. Hands-free equipment takes the hand out of the problem but not the attention: the conversation still competes with the road for it. The safe course is to leave the call until you have stopped somewhere safe, or to let it go to voicemail and listen to the message later.
Anything else that pulls your eyes off the road belongs under the same rule. A screen, a music system you are searching through, a passenger's phone held up for you to look at, all of them take the road out of view for the seconds in which it changes. Set up what you need before you move off.
Passengers help by not distracting the driver, and a driver can help by asking for quiet where the traffic is difficult.
Do not use a cellular phone at a filling station. Switch the engine off while refuelling, and do not smoke or strike a match at the pumps.