Making a voice call can still be difficult in some areas
UK mobile operators need to do more to help customers who experience coverage problems, an advisory panel has said.
It recommends a "try before you buy" period in mobile contracts to enable customers disappointed by their new handset's coverage to switch operator.
The Communications Consumer Panel, which advises Ofcom, says about one-third of consumers and small businesses regularly experience coverage problems.
One operator said many factors "outside our control" could affect coverage.
Communications watchdog Ofcom recently pledged to investigate why there are such gaps around the UK.
"While all the focus is on rolling out new services like mobile broadband, our research reveals that large numbers of consumers and small businesses are still having problems making even basic voice calls," said Anna Bradley, chairwoman of the Communications Consumer Panel.
"It is essential that consumers aren't trapped into contracts that don't give them the coverage they need," she added.
Researchers found that more than half (56%) of consumers and 91% of small businesses have difficulties with mobile coverage, with a third of all those surveyed saying it was a regular experience.
Mobile coverage problems are not limited to rural and isolated areas with some city-dwellers also struggling to get good connections, the survey suggests.
The quality of coverage depends on a number of factors, including how near a person is to a transmitter, whether people use their phone inside or outside, the local landscape and even the weather.
O2 said that it already offered a "try before you buy" contract.
"We offer a 14-day cancellation policy for our mobile services. Customers buying directly from O2 may cancel their contract and return their SIM card and handset within 14 days," the firm said in a statement.
"In addition, for home broadband and mobile broadband, we offer a 30-day happiness guarantee, which allows customers to try the service at home and in their local area."
Orange said its GSM network covered 99% of the UK, while its 3G service covered 93%.
It said it offered prospective customers the chance to find out about the level of coverage in their area through the Orange coverage tracker.
But, it said in a statement: "Local and physical conditions, such as building materials and atmospheric conditions, or environmental obstacles like tunnels, dips, cuttings and wooded areas can interfere with radio signals and impair mobile reception strength for all mobile networks.
"As such, no mobile operator can guarantee continuous network coverage, which can be affected by factors outside our control."