Many users of mobile phones in the UK are paying too much for their service because call centre staff at the service providers do not know what their own tariff systems are.

Staff at O2 were the most likely not to know the answer to price enquiries from customers and potential customers, while those at Virgin were the most accurate, followed by 3, T-Mobile, Orange and Vodafone.

These were the findings of a survey of the UK’s top six mobile firms undertaken by Onecompare.com, although O2 refuted the findings and said that the survey was not broad enough to draw an accurate conclusion.

“We do not think that Onecompare are right to draw a conclusion based on a sample of just 100 calls,” said a spokesperson for the company.

“We receive an average of 150,000 calls per day, which means we received over 8 million calls in January and February of this year.

“We will study the survey’s findings more closely, as they contradict the independent recognition we have been receiving for the quality of customer service we do deliver.”

He continued: “We continue to make heavy UK investment in making sure that our customers get the best possible service, which includes the recent opening of our fourth customer services centre in Glasgow.”