Vodafone and EE have been given the thumbs down in a customer satisfaction survey where they have come second from the bottom.
They scored 49%, just above the international calls specialist Lebara at 46%, in the Which? annual mobile satisfaction survey.
Vodafone was the most complained about pay-monthly mobile provider while one in 10 EE users rated customer service and the ease of getting in touch with the company as poor or very poor.
The 4,101 members of the British public who took part gave star ratings on a range of factors including customer service, ease of contacting, value for money and incentives. Their level of satisfaction and how likely they were to recommend it to a friend were taken into account.
Giffgaff, which has no shops or call centres, topped the table for the second year running with 79%. The online provider's low prices plus flexible approach to selling pay-as-you-go (PAYG) Sim cards and unlocked handsets that can be used with any network proved popular.
Supermarket providers claimed the second and third spots. Asda Mobile scored 72% while Tesco Mobile recorded 70%.
Asda Mobile's good standing may have been boosted by a PAYG service which was rated highly for value for money, according to the survey.
Among the providers, ID scored 64%, Virgin Mobile 62%, Three 61%, O2 60%, Talk Mobile 56% and TalkTalk got 54%.
Alex Neill, campaigns director of Which? who estimate that mobile users are collectively losing out on £5.4 billion a year by being on the wrong contract, said: "Our latest survey once again shows that the major mobile providers are still failing on the basics of customer service. Telecoms are an essential part of modern life and so providers need to start delivering for their customers."
Zen International topped the broadband provider table with 83% satisfaction rating, ahead of Utility Warehouse at 80%.
The 3,717 broadband, phone and TV customers who took part were questioned about annual cost, ease of set-up, speed, reliability, value for money, ease of contacting, customer service and technical support.
Plusnet came third with 65%, just ahead of John Lewis Broadband at 64%, Post Office at 59%, Vodafone at 58% and Virgin Media at 54%.
Customers gave Sky a 50% satisfaction rating while EE Broadband got 49%, BT 47% and Talk Talk were at the bottom with 38%.