British Gas's second cut in charges this year has tempted almost a million customers to return.

But that has not stopped complaints pouring in about inaccurate billing, delayed refunds and poor service from the company.

The energy giant has cut electricity rates by a further 6 per cent and gas by 3 per cent, which will reduce the average customer's bill by £40 per year. Add that to the cuts it announced in March, and the average dual fuel customer could save over £200 per year.

The cuts are seen as a partial victory for consumers who have long complained about high prices and poor service. "This second cut by British Gas demonstrates that consumer power really does exist," says Geoff Slaughter, energy product manager at service switching provider uSwitch. "It seems to be a direct response to its customers."

Many argue the cuts are simply a knee jerk reaction to a scathing report from consumer watchdog, energywatch, on British Gas's substandard customer service levels. Karen Darby, founder of switching website SimplySwitch comments: "These cuts are not huge, but this is a welcome, if tactical step. British Gas was criticised for its customer service record, so the energy company acted in the swiftest way it could - by cutting prices."

And what a customer service record - figures from energywatch show more than 21,000 complaints were made about British Gas in the six months from October, 2006, and March, 2007. That far exceeds the figures for EDF Energy, npower, Powergen and Scottish Power. British Gas may have only 30 per cent of all gas and electricity accounts in Britain, but it gets more than 70 per cent of the complaints.

"We reported six months ago that British Gas had the worst customer service in the industry," says Adam Scorer, director of campaigns at energywatch. "Their service has gone from bad to worse."

Most of the complaints were related to billing. Ever since British Gas introduced a new billing system problems have escalated. The company claims it reviews customers' bills and usage several times a year, but many people still find the amount of energy they use is over-estimated and their payments too high.

Many direct debit customers with a surplus on their account are chasing refunds, and complaints about refunds being ignored or delayed for months have flooded energywatch and consumer websites.

A spokesperson for British Gas acknowledged there have been teething problems with the new billing system. "The implementation of the new system across millions of accounts has led to problems," she says. "I must stress that the vast majority of account holders have not had any problems, but for the few that have we know this is not good enough. We are investing a lot of money into putting it right and have recruited an extra 800 people."

Regarding complaints about refund delays she says the company reassesses accounts every three months, and if customers are more than £80 in credit after 12 months they automatically receive a refund.

If you are dissatisfied with your current energy provider you can make a complaint to energywatch. But the watchdog stresses they cannot help unless you contact your supplier first and give them the opportunity, around ten days, to resolve the problem.

You can also switch suppliers using one of the comparison and switching sites. However, don't be tempted solely by the cheapest deal - cheap prices aren't much good if the supplier charges for energy you have not used. Consider the quality of service too.

Try the following to take back control of your bills: Take regular meter readings. Unhelpfully, providers are required by law to read the meter just once every two years.

Paying by cash or cheque means you only pay for the gas and electricity you use. But be aware it may be more expensive as some energy companies offer a discount for paying bills by direct debit.

If you are having problems getting a refund after being overcharged, switching your supplier should speed up the process when you cancel your account.