UK iPhone customers are furious with O2 over suggestions that those wishing to upgrade to Apple's new iPhone 3G S face a bigger-than-expected outlay.

Announced at Apple's Worldwide Developers Conference yesterday, the iPhone 3G S will be available in the UK on 19 June and pricing information is now available on O2's website.

However, current iPhone owners are outraged at a reported O2 iPhone 3G S upgrade path that may require them to pay the remaining cost of their contract, plus the cost of the newer handset.

iPhone 3GS Many iPhone 3G owners signed up to an 18-month contract when the phone was launched last summer, but believe O2 should allow them to escape the remaining six months of their deal if they commit to a new long-term contract for the 3G S.

"This is so dumb, I was happy to upgrade each time and sign up for another year, not now, if this happens, when my contract's up, I'm unlocking and never coming back," said one user on the O2 forums.

Another user has set up a petition elsewhere on O2's forum trying to convince the operator to rethink the UK iPhone 3G S's upgrade charges.

"I know you are a business, here only to make a profit. I get that, I honestly do," says the petition. "It would seem, however, that you have one small gap in your knowledge base. The Apple user. Fiercely loyal, intelligent and not afraid of a fight - they like the latest equipment but hate to be ripped off for it.

"You gave new adopters no choice but to agree to an 18-month contract on a phone that would be replaced within 12 months.

"Maybe, just maybe, the loyalty of these users is worth some consideration. I doubt many would expect to be let out of their contracts freely, but a little compromise goes a long way."

UK O2 customers will also have to pay to use the iPhone's new internet tethering feature, which turns the handset into a 3G dongle for a laptop. The feature, added in Apple's new iPhone 3.0 software update, works with the iPhone 3G and 3G S but costs £14.68 for 3GB of data per month, or £29.36 for 10GB of data.

iPhone 3G S: new features

The highly anticipated iPhone 3GS, which will be available in 16GB and 32GB versions, promises to launch applications and run software faster than the previous model.

"The 'S' stands for speed," Phil Schiller, Apple's senior vice president of worldwide product marketing, told Worldwide Developers Conference attendees during yesterday's conference-opening keynote.

While the iPhone 3G S looks similar on the outside to the previous 3G model, the new phone offers a brand-new camera that lets you control the focus either by tapping on the screen or using the autofocus feature. In addition, the iPhone's new camera captures video in addition to still photos - a heavily requested feature among iPhone owners.

In addition, the iPhone 3G S includes a voice-control feature to allow users to speak commands for applications on the phone. Accessibility improvements include VoiceOver support for reading to users and the ability to zoom in on the phone's display for larger icons.

Business users get a requested feature in the form of hardware encryption. For anyone using an Exchange service of the Find Your iPhone feature in the iPhone 3.0 software update, remote wipe is instantaneous and backups are encrypted.

Apple also promises improved battery life with the iPhone 3GS. The new phone offers nine hours of internet access on Wi-Fi, 10 hours of video, 30 hours of audio playback, 12 hours of 2G talk time, and five hours of 3G talk time.