Apple and O2 have confirmed user reports of being unable to make or receive calls, use text messages, or get a reliable 4G internet connection, exclusively on the iPhone XR.
"We are aware of an issue causing intermittent network connectivity effecting some O2 customers," an Apple spokesperson told BBC News, "and we will have a fix in an upcoming software release."
It's not known how many users were affected, but customers told the BBC that problems began some weeks ago. Certain users are saying they noticed a problem in late November, and iPhone XR owner Jim Buckley told BBC News that it began on December 16.
"I've had virtually no signal at all since," he said. "It may come with a weak signal for a few minutes once or twice a day, then go again."
"We're working closely with our partners to resolve an intermittent issue affecting some of our customers using iPhone XR," said an O2 spokeswoman. "We thank any customers affected for their patience."
When the iPhone was launched in the UK in 2007, it was exclusively on O2. The carrier remains one of the few that supports all the iPhone features, such as visual voicemail.