I received this via email, never encountered it myself though...

I don't know enough about the telecom systems in Europe to judge but there have been some like that in North America.

The US, Canada, and some other parts of North America use the North American Numbering Plan (NANP) in common for assigning area codes and phone numbers. The US and Canada have adopted very similar regulations but some of the Caribbean islands have not. This can result in people in the US dialing a number and not realizing that it is not only an international call but also directed to a very pricey pay-for-service number in the other country. Naturally, the "bait" emails mentioned nothing about this.

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MS MVP Security 2006-2008

We get a lot of these warnings over here, most turn out to be false alarms. The 07090 number is a standard mobile number, all mobiles (cell phones) have 07 numbers in the UK. I can't see a reason why this would amount to a £250 charge. If the phone was being used from abroad, it would require the addition of an international dialling code.

Whatever comes or goes, if it were a genuine prize, the caller would be a real person. Safest bet is just to end the call immediately.