The UK's largest mobile network operator also has the biggest number of disgruntled customers, according to research released by communications watchdog Ofcom.
The regulator said EE had achieved an overall customer service score of 69%, not far below the 2014 mobile sector average of 73%.
O2 came out on top among mobile providers with an overall satisfaction score of 78% and was rated as above average on criteria including ease of making contact, usefulness of information and logging of query details.
Satisfaction across the mobile sector fell slightly from last year's score of 75%, though satisfaction among those customers with a complaint has increased by 13 percentage points since 2011, to 59%.
Ofcom also questioned consumers about their fixed broadband providers, landline providers and pay-TV services.
It found that overall customer service satisfaction remained lower in the fixed broadband and landline markets, at 69% and 67% respectively, compared with pay-TV at 80%.
The figures were based on interviews with thousands of customers who had contacted their provider between July and September this year and were asked to rate their customer service experience, based on a combination of the speed with which issues were dealt with, the standard of advice given, and the attitude and ability of the advisor.
Sky bested Virgin Media in the pay-TV category, with a score of 81% compared with Virgin's 78%.
Ofcom reported the main reason for consumers contacting pay-TV providers was to discuss changes to their package or service.
It also noted a rise in bill shock. "There was also a significant increase in the proportion of contacts from consumers relating to higher bills than they'd expected (5% in 2013 to 9% in 2014)," Ofcom said.
Ofcom's research covers customer service satisfaction for those providers with a market share of 4% or more.