Vodafone has been rated the worst mobile phone provider for the seventh year running in an annual customer survey by consumer lobby group Which?.
The other leading providers, EE, 02 and Three, also scored badly, with service judged "average" and "disappointing".
Of the small providers, Utility Warehouse ranked highest for value for money, incentives and customer service.
Vodafone said improving services for customers was a top priority and it had been working hard to address the issue.
It said in a statement: "These findings published by Which? really don't match up with what our customers are telling us, with our own, independently verified customer satisfaction scores jumping 13 points from last year to their best ever level."