AT&T customers in southern California experienced a service outage lasting from Saturday afternoon through to Sunday.
The problem, which at its height affected about 1,000 cell towers, is said to have been caused by mechanical problems with the switching equipment that routes calls through the network. Most of the affeected towers handled calls to and from LA County and Orange County.
The problem started about 3pm. Six hours later, the company confirmed on Twitter: "Los Angeles area AT&T customers may have issues with wireless service. We are working now to resolve. We apologize for any inconvenience."
By then, the outage was one of the top trending topics on Twitter, with hundreds of disgruntled customers reporting dropped and failed calls as well as an inability to access voicemail. It's not known how many users were affected.
Data and text services continued to function normally.
Service was restored for most customers by yesterday morning.
AT&T's apologised for the disruption.