A slightly different version to the Florida holiday competition scam which only has the intention of grabbing your card details.
There are too many unscrupulous businesses being allowed to operate Merchant Trader Facilities (providing the ability to process Debit and Credit Cards) and, of course, they have no justification for processing card details obtained fraudulently, whether the person gave details willingly or not. If a company trades dishonestly not only should the card payment be reversed, but they should have their facility terminated, but too many banks nowadays are being lax.
The quick solution is never to give your personal information of any sort to any stranger who rings you out of the blue. I've had calls purporting to come from my isp in India, and they had details of my account, but I wouldn't discuss anything with them. I told them to put it in writing, and I never heard any more. Offshore offices in India are notoriously 'leaky'.
Non-EU citizens should go here to find out about obtaining a visa to work as an au pair in the UK
http://www.ukvisas.gov.uk/en/doineedvisa/
Whenever payment is requested by Western Union you're dealing with a scammer
