I don't think Natwest have a call centre in India, but it could happen anywhere. From the BBC News site..
http://news.bbc.co.uk/2/hi/uk_news/4121934.stm
Police are investigating reports that the bank account details of 1,000 UK customers, held by Indian call centres, were sold to an undercover reporter.
The Sun alleged the computer expert told the reporter he could sell up to 200,000 account details, obtained from fraudulent call centre workers, each month.
Details handed to the reporter had been examined by a security expert who had indicated they were genuine, the paper said.
The information passed on could have been used to raid the accounts of victims or to clone credit cards.
The allegations in the Sun follow the April arrests of former call centre staff in western India in April.
They were said to have obtained passwords and then after leaving the company transferred money out of customer accounts.