Phone users could be paying more than they need to and receiving worse service by staying with the UK's biggest mobile networks, consumer expert Which? has said.
O2, EE, Vodafone and Three ranked lower on customer service and value for money than lesser-known rivals, according to a survey of phone users.
This is despite virtual networks using the same phone masts and other infrastructure as the so-called Big Four, rather than running their own services.
Three scored the lowest of the Big Four and received the lowest rating out of any network for reliability while nearly half (45 per cent) of its users experienced problems in the past year compared to three in 10 (29 per cent) across all mobile network customers surveyed.
Virtual network Smarty uses the same infrastructure as Three but came first place in the table with five out of five stars for value for money.
The largest UK network, EE, came 11th out of the 16 providers analysed with users reporting mediocre customer service, technical support and value for money. The network's download speeds was the only category to gain a four star rating. The Big Four providers currently service three quarters (76 per cent) of customers in the UK, according to Ofcom.
But consumer champions Which? say the flexibility offered by virtual networks keeps mobile costs down and could better support consumers facing a household budget squeeze.
It found customers pay on average almost £10 a month less than Big Four customers across all contract types.
Natalie Hitchins at Which? said: “The vast majority of mobile users are with one of the Big Four providers, but our research suggests consumers could save money during the cost-of-living crisis and get better service by switching to one of the networks challenging their dominance.
"Anyone looking for a reliable carrier that offers a flexible contract and good value for money should consider one of the virtual networks, who continue to outperform the Big Four year after year."
Which? said customers of the Big Four experienced price hikes of up to 11 per cent but remained the most loyal, with more than half of EE, O2 and Vodafone users being with the provider for more than five years.
Experts warn these longer-staying customers are likely to be paying more than they need to for their phone contract. Which? suggests challenger providers have an edge over bigger players by focusing on rolling monthly sim deals over phones with lengthy contracts.
An EE spokesperson said: “EE customers enjoy being part of the UK's biggest and fastest network with more 5G coverage than any other provider and EE has been named the UK's best network for the past eight years by RootMetrics.
“We provide the best customer service across the industry reflected in the most recent Ofcom complaints data”.
Three and O2 were contacted for comment.
