O2 yet to resolve iPhone data roaming glitch
The mobile operator O2 says it is still investigating iPhone customer complaints that they have been wrongly charged for data roaming while abroad.
Customers have complained that the switch that deactivates data roaming doesn't work, a fault O2 was first made aware of in May.
Neither of the other UK networks that carry the iPhone, Orange and Vodafone, says it has been hit with the problem.
Apple forum posts suggest the problem may lie with O2's "visual voicemail".
The fault can cause big bills for customers who receive emails and web pages when they are overseas - even though they didn't choose to receive them.
The default setting on the iPhone should prevent data from loading up abroad. However, customers on the Apple and other forums are complaining that e-mails and web pages are sometimes downloading when they are abroad - even when the data roaming setting is off.
O2 says it is "investigating these reports with Apple".
One recent post on an Apple online forum reported that: "Even with data roaming off, I received a visual voicemail message which appeared to then trigger the downloading of 25 e-mails and enabled selective web browsing and app activity. I'm going to call my network operator (O2) tomorrow, but others have complained about this bug that first appeared with the 3G iPhone and was fixed by an update."
An Apple spokesperson told BBC News that "we are aware that some O2 customers have reported receiving unexpected data roaming charges and are investigating. To avoid unexpected data roaming charges while traveling outside the UK, O2 customers can turn off Cellular Data in their iPhone settings."
Adrian Mars, an independent technology journalist, said he has some sympathy with the mobile operator.
"The big problem here is that Apple has a policy of not admitting to known faults in the phone so the operators are really stuck," he said
"They don't know whether there is a fault there."
O2 will be faced with a difficult choice in deciding whether to refund customers who complain they have been hit with undeserved data roaming charges, as Mars acknowledges.
"It's terrible. Looking at the bulletin boards, some have got their money back; some are saying they have.
"But until Apple holds up their hands and say these are the circumstances when it happens it will be very hard for them to know what to do."