O2, the original carrier of Apple's iPhone in the UK, has been hit by connectivity and service problems since the weekend.

O2 used Twitter to inform users of the problems. "We're sorry that some mobile customers have had problems with data today - these services will be back up tonight," the O2 Twitter feed noted on Sunday evening.

On Monday, an update followed: "We apologise to customers who cannot use data at the moment. We have a fault with the allocation of IP addresses which we are fixing."

O2 was not alone in using Twitter to highlight the problems. "My iPhone is refusing to connect with the cellular data network despite a healthy 3G interface. Any ideas?" Shaun Of The Dead star Simon Pegg tweeted.

"Seems to fixed. Am able to tweet and go again. How quickly we learn to rely on things we don't understand," Pegg later reported while marvelling the festive snow in London's Crouch End.

Several Macworld readers also sent emails to highlight the problems. "I just called and asked the agent if they could pass a message onto the relevant people and request a message be placed on O2’s website informing customers of the problem, what the issue is, and when we may expect a fix," said a frustrated Lee. "He wasn’t interested, in fact his reply was find a Wi-fi spot and then the phone when dead."

Helen was told to change APN settings on her iPhone. "Go to Settings > General > Network > Cellular Data Network and change idata.o2.co.uk to mobile.o2.co.uk," a change which had previously resolved the issue. However, this time around, changing the APN settings did not fix the problem for everyone.

"When I asked if 'pay monthly' customers would get compensation for the outage of the data network, I was told that I should take that up with O2 when everything is back to normal," added Tom.

O2 has used Twitter to update customers.

In a statement O2 told Sky News Online yesterday: "We are aware of an issue currently impacting data access for some of our customers," having identified the fault with the allocation of IP addresses.

Two O2 updates followed on Monday via Twitter. "Quick data services update: the system fault has been fixed and internet connections are gradually being restored," and "MMS and Visual Voicemail remain affected - we’re working on these as a priority." More updates are being added on Tuesday morning, O2 denying in a tweet that some responses had been sarcastic. "No sarcasm, just offering alternatives if there are problems."

O2 announced just after 4 pm on Tuesday via Twitter: "Data network update: Visual Voicemail is now working."

O2 customers have suffered problems with lack of Internet and email earlier this year, in July and August for instance, when the company apologised for a poor and patchy service.

Since then, O2 now has competition in Orange, Tesco Mobile (potentially cheaper option but same O2 network) and from 14th January Vodafone. O2 customers at the end of contracts may need to take their custom elsewhere if the problems persist.