O2 customers with the iPhone XR are being kicked off the internet, they say.
A variety of users complain that they lose connection several times a day, apparently for no reason.
Some of them have been suffering with the problems for weeks, they say.
Switching the phones off does appear to fix the issue. But only temporarily, and it will return soon after, affected users say.
The issue appears to be specifically related to the way that iOS on iPhones that are on the O2 network.
That means it will be fixed through an update from Apple. The company says it is working on a resolution in an upcoming software release, but it is not clear when that will arrive.
"We're working closely with our partners to resolve an intermittent issue affecting some of our customers using iPhone XR," O2 told customers.
"In the meantime, please turn the device off and on to restore the signal temporarily."
The iPhone XR is one of Apple's most popular devices. It was the cheapest of the three phones it released in 2018, and is still on sale.
