If ever you receive a call like this, and you find that it starts 00234 (for the UK, other countries will be different, but this part of the number will end in 234), then DO NOT return the call. Obviously, if you have friends or relatives who live in Nigeria and they phone you, you will know their number and can recognise it. Like scam e-mails, where they use social engineering/manipulation techniques in persuading you to yield personal information, this is another method. This type of phone call originates on automatic dialing machines, whose sole purpose is to randomly dial numbers anywhere in the world. It also listens for any replies from people who choose to reply. The reason why they tend to ring just once is so that it doesn't cost them anything - you only get charged for calls when they are answered. It then saves the numbers of people who reply, which are then given to other scammers, meaning that if you do reply you will more than likely get a huge increase in this type of call, both from Nigeria and elsewhere.