Energy firms are not just making money from customers by ramping up prices. They are failing to answer phone calls promptly, in some cases charging as much as 55p a minute for those who hang on.
A recent survey by consumer group Which? found that supplier Spark Energy takes an average 30 minutes to answer customers' calls.
Eon makes customers wait more than 14 minutes while British Gas customers must hang on for nearly ten minutes. The energy industry average is just over three minutes.
Some suppliers, such as Eon and SSE, use '0345' customer service numbers – which charge callers from a mobile a fee of up to 55p a minute.
Katy Cavell, from Chesterfield, Derbyshire, left British Gas last November after receiving poor customer service.
The 31-year-old pharmacy technician says: 'I rang up to ask if I could be put on a better deal.
'After waiting ten minutes and navigating a maze of voice-recorded options I got through to a person who said, 'It [my current bill] is what you are using.'
'With that kind of unhelpful response and service it was time to quit.' Katy ended up switching to Octopus Energy, not just on cost grounds but also customer service ratings.
Edward Molyneaux, of energy comparison website The Big Deal, says customers should not opt for a supplier just on price.
He says it is important to look at customer ratings before switching.
He says: 'Customer service issues are not confined to the big six suppliers.
'If a fledgling firm picks up lots of new business, its service levels can fall. That s why it is crucial to check feedback from existing customers.'
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