Keallhauled has found that a Telecom XT Sim card will run fine in an iPhone bought from Vodafone, with just a simple DIY setting change.

However, the release of iPhone OS 3.0 has muddied the appeal of network hopping using Apple’s handset. With this operating system software upgrade, free via the iTunes AppStore, you gain the ability to tether, or use your iPhone as a modem.

Some people using the iPhone with an XT Sim card have been able to tether - as relayed in this Geekzone forum discussion pointed out by IT consultant and commentator Colin Jackson.

However, it does seem that unlike voice and data on the iPhone, tethering is something that has to be activated via carrier setting that you download from iTunes.

Telecom is not an official Apple carrier (yet) so has no settings for download on iTunes.

On Geekzone, you’ll see some clever types have created their own “carrier pack”. Download it, and apparently you can tether.

“Several people have told me that this works,” Mr Jackson emailed Keallhauled.

“However, the Telecom patch comes from a third party website, comes with a complex install procedure (downgrading iTunes first), and warns that it may break roaming and other undesirable behaviour. That, and not wanting to break my iPhone from running on Vodafone, is why I haven't tried it,” Mr Jackson wrote.

“This undoubtedly works, as various people have told me. But it's rather dubious status means that I think you'd be brave to rely on it, or to do it to your primary phone.”

Telecom - which had been eager to facilitate a demonstration of a Vodafone iPhone running on an XT Sim for regular use - had not comment on tethering.