To Michael Joseph’s frustration, his customers keep flashing. At all times of the day. For no more than a second but long enough to catch each other’s attention. In Kenya, where his company Safaricom is the dominant mobile phone operator, it has nothing to do with indecent exposure.

To flash is to call a mobile and hang up before the call is answered, a cost-free way of letting the owner know you want to be called back. People do it because they are low on pre-paid credit, or because they think the other person has a better reason to pay for the conversation.