Vodafone has become the UK's most complained about mobile phone provider following a surge of complaints in the final months of 2015.
The UK telecoms watchdog Ofcom has said it recorded 32 complaints for every 100,000 of Vodafone's pay-monthly subscribers in the last quarter of 2015. This was a major surge, more than double the amount of complaints recorded in the same period of 2014, although Vodafone was still the most complained-about provider the previous year.
The company was the only provider to have more complaints than the industry average of 10 per 100,000 customers, Ofcom added.
The complaints about Vodafone's service included grievances related to charges, billing, pricing and complaints about the company's complaints handling procedures.
Vodafone blames the negative feedback on an IT glitch relating to a major and "complex" £2bn programme the company undertook last year to transfer customers on to a new billing system. According to the company, it has around six million consumer pay-monthly subscribers, equating to a third of the UK's total customer base, which stands at 18 million.
The only other mobile operator to experience a rise in pay-monthly customer complaints over the last quarter of the year was Talk Mobile, although it registered a much lower figure of nine complaints per 100,000 subscribers.
Tesco Mobile was the consumer's favourite over the period, generating just one recorded complaint in every 100,000 customers.