Many cash back deals are not made with the service provider themselves but with the individual outlet, which means that if the shop selling the phone goes out of business, the customer loses their entitlement to get their money back.

One Citizens Advice customer lost hundreds of pounds when the company who sold him a £75 contract for £9.99 a month went bust – and the network provider refused to honour the deal struck with the intermediary.

“People are attracted to these deals because they appear to work out much cheaper than other mobile phone packages,” commented Citizens Advice social policy officer Susan Marks.

But she warned customers: “Don’t be tempted to pay up front on the promise of cash back in the future unless you’re prepared for the possibility that you may never see that money again.”

The Office of Fair Trading has just launched Scams Awareness Month, alerting British consumers to the £3.5 billion lost each year by consumers duped by false promises.

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