Picture the scene: you open up what you think is a routine letter from your credit card provider and find that the nice, low rate you have been paying is no more.
Suddenly it's going up by several percentage points – but this is not happening to everyone, just to those who the provider thinks are now a higher than normal risk.
It is a slap in the face which is exactly what is happening now to thousands of customers of Virgin Money.
"Those who signed up to a competitive credit card rate in a bid to sort their finances may now be stuck on a high interest card which could make their payments unaffordable once again.
"The message from Virgin seems to be if you can't put up, you have to pay up," says Michael Ossei. a personal finance expert at uSwitch.
Virgin claims that only a small fraction of its customers are being hit by the rate hike, but with other providers waiting in the wings to repeat this unwelcome move, what options do you have should you find yourself targeted in this way?
"I think the practice of reassessing and bumping up borrowers' rates is fairly widespread throughout the industry, but nobody is aware apart from the individual cardholder concerned, unless someone reports it to the media," says David Black, a banking analyst at financial information service Defaqto.
Sometimes, though, the rate increases can be substantial and thousands of card holders are targeted.
"Two high-profile examples were Egg in 2009 which increased interest rates on half a million credit card accounts by up to 7 per cent – blaming rising internal costs and funding costs – then, a year later, Capital One raised some rates more than 7 per cent – blaming the increased risk of lending in an economic downturn," Mr Black said.
"It can seem very unfair that you have seemingly done nothing wrong and your agreed rate is going up. This can be due to the provider suddenly moving the goalposts and reassessing the credit worthiness of customers. When this is done some customers naturally migrate to a higher rate," Mr Black added.
So what should you do if you're unlucky enough to get a letter telling you your rates are going up?
"Well, first things first, it's important to realise that you have the right to reject the increase provided that you do not make any further transactions with the card. If you keep to the terms and conditions – make monthly repayments on time, for example – you continue to make repayments of the outstanding balance on the card at the existing rate of interest for a reasonable period," says Andrew Hagger from financial advice site Moneynet.
If banks want to raise the interest rates, cardholders must be given 60 days to accept or reject the change.
If a customer does not accept the increase, they can choose to close the account and pay off what is left in instalments as long as it is at least the minimum monthly payment, rather than a single lump sum, and at the current rate of interest.
If you can't simply stop using your card then the options are to either accept the new rate or move your balance to a cheaper credit card.
However, it can be hard to find a more competitive deal.
"It is becoming much more difficult to get a new credit card as lenders have really tightened up their underwriting and acceptance criteria over the course of the past few years," said Mr Hagger.
"Increasing numbers of consumers are unable to get a credit card and have effectively become excluded from mainstream credit."
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