Help! My iPhone is burning a hole in my pocket

The man on the other end of the phone sounds desperate. "Can I ask why you want to leave [mobile phone provider other than O2]?" he says. Yes, I tell him. I'm afraid I want to buy an iPhone – and I've been waiting for my contract with you to end for some time so that I can do just that. "But," he pleads, probably not for the first time today, "we have phones that are better and cheaper!"

The sad thing is I believe him – well, the "cheaper" part, anyway. "I'm sure you do," I reply soothingly, trying to soften the blow of my departure. I've gladly remained with the same network for about 11 years, the entirety of my mobile phone-bearing career; but, as I tell the increasingly-agitated customer services representative, the allure of the glowing white apple has me hooked. Until the recent introduction of the new 3GS handset, it felt like a niche product. Now, however, half of my friends have one. The iPhone has reached its tipping point, and I have to own one, too.

That means switching to O2, which (so far) retains its exclusivity deal with Apple in the UK. What O2 doesn't tell you, however, is that after you've signed up with them – for about £15 more per month than I was previously paying – your iPhone will continue to cost you money. Lots of money. I don't blame the company, though, only myself; the iPhone is a desire, not a necessity, as are all its added costs.

As an O2 spokesperson assures me, the iPhone is "a revolutionary device that is far beyond just a mobile". With a phone, MP3 player, camera, web browser and email inbox, plus free, unlimited Wi-Fi and data, it's a mini computer that makes my netbook (the last tech bandwagon I just had to leap onboard) essentially redundant. Don't get me wrong, I love the thing, but I have consumer anxiety nonetheless.

The £87.11 I pay for the 3GS and the £34.26 per month tariff are only the beginning. First of all, I have to sign a two-year contract. Of course O2 wants to ensure they recoup the costs of subsidising the iPhone for its customers, but they also know mugs like me love shiny technological gizmos enough to lock themselves in until 2011. And since I'm convinced that, during its lengthy lifespan, this digitally-intricate little bundle of joy will develop a few health problems, I add £10 of insurance costs to my monthly bill.

For the same reason, I go straight out and buy a rubber sheath to protect it from bumps and grazes. It's white, which should be deeply Apple-retro (and match my MacBook laptop). Instead it looks rubbishy and cheap and contains at least one crucial design flaw – the rubber covers the earpiece, making telephone calls somewhat lopsided. So I go out and spend another £20 on a different case.

Once you start collecting iPhone accessories, you could go on forever. Belkin, one of the leading manufacturers of computing peripherals, has a range of iPhone add-ons including everything from cases and sports armbands to extra electronic devices such as headphones splitters, FM radio transmitters and portable chargers. The company is the biggest player in an iPhone/iPod accessories market that Gary Tubb, Belkin's Managing Director for the UK and Ireland, estimates is worth approximately £50m.

"It's been huge for us as a business," says Tubb. "Wherever there's an iPhone accessory to be had, you'll find the Belkin brand. The more successful Apple is, the more successful we are. There are some brands who do nothing but create accessories for the iPod and iPhone."

Once you've got all your peripherals sorted, it's time to start acquiring applications. There will probably be 100,000 iPhone apps on sale by the end of 2009, and apps downloads from Apple's App Store recently passed 1.5bn. To begin with I add only free apps to my iPhone and find it scarily straightforward.

They were enough to keep me occupied for all of about 10 days, until a colleague tells me about WunderRadio, which would allow me to listen to Radio 4 while showering after my cycle to work. That sets me back £3.99, which on its own doesn't sound like much, but I dread the day I wake up after one too many drinks to find I've binged on the likes of Sonic The Hedgehog (£3.49) or Let's Golf! (£1.19).

All the while I'm worrying that, over the next two years, other, better, devices will appear on the market, and I won't be able to get my hands on them. "Right now, the iPhone is the benchmark for such devices," says Tony Cripps, an analyst with technology consultancy Ovum. "But some of the recent devices with the Android operating system are pretty good, too. And they ought to end up having a more widespread appeal, because in time there will be more devices with that software platform. Apple has the most apps now, and a head start on the work Android, Nokia and Microsoft are all trying to do, but they're all heading in the same direction and the others will quickly mature."

Any phone with iPhone-like capabilities remains fairly expensive, but it's fair to say the deals being offered by T-Mobile and Orange for the HTC Hero handset (aka the G2 Touch), which uses the Android OS, are more competitive than my iPhone deal. They're cheaper than my iPhone. Could they be better? And never mind Android phones. If I'm stuck with my 3GS for two whole years, won't a better model – or two, or three – come off the Apple conveyor belt in that time?

The original G iPhone had to be bought separately of the network contract. Its successor, the 3G, was subsidised by O2, but customers with a G were allowed to upgrade early. When the 3GS was released this summer, users were denied the same automatic upgrade, much to their disappointment. O2 insists, however, that anyone spending over £35 per month on their contract can indeed upgrade early from the 3G to the 3GS – between one and six months early, depending on how much they spend.

There are, reportedly, "4G" prototypes in existence. One Chinese Apple worker committed suicide last month after the 4Gs for which he was responsible went missing. Do I really want to spend more to guarantee myself a 4G upgrade in, say, a year's time?

Cripps tries to reassure me. "The key to these devices is that the software is upgraded remotely by the manufacturer over time," he explains. "When you eventually give up your iPhone 3GS, it won't be the same device you started with. Apple have updated the firmware on the iPhone already, and each time that happens you ought to see a marked improvement in your handset.

"It's no accident that all iPhones to date look the same. Apple could go the other way and have endless handset designs, but then developers would have to make content that ran on different devices, with subtly different software and requirements.

"In order to produce the iPhone's tidy, integrated environment, Apple has simplified the OS and limited the freedom they have in terms of hardware design – but that's probably a good idea. If you're concerned that within two years a next generation iPhone will come along that makes you say, 'Ooh, I have to have that,' I don't think that problem will arise."

Mobile must-haves? The iPhone accessories you never knew you needed

iWood

Not satisfied with rubber or plastic? Never fear; you could also encase your precious iPhone in mahogany, courtesy of the iWood, a hard case available in six different woods, for only 70 quid. A wooden iPhone pouch is in the works, too. Miniot.com

Gelaskins

Isn't your iPhone beautiful enough for you already? No? Then you need to personalise it with these wraparound iPhone stickers. They even come with matching downloadable wallpapers. Make your handset unique! (Or, at least, as unique as every other item in the world with a Keith Haring-inspired design on it.) Gelaskins.com

Lego speakers

Maybe you've already got some speakers for your iPhone. But I'll bet you don't have speakers that look like Lego bricks. Who cares what the sound quality's like, they look awesome ... Coolest-gadgets.com

iPhone Stylus

Are your hands too chubby to manage your touch screen's qwerty keyboard? Why not buy yourself a stylus, specially designed for the iPhone? It's better than your fingers. Until, of course, you want to use the double touch function to zoom in or out. But hey, why not buy two? Uk-mobilestore.co.uk

Charging shelf

Don't you just hate having to find a socket with a suitable spot nearby to rest your iPhone while it charges? Now you won't have to, thanks to this handy charging shelf. It comes in seven colours – including mango! Charmingcards.com