An iPhone blogger has revealed a way of legally unlocking the device after paying off his mobile contract.

TheAppleBlog.com’s Olly Farshi claimed he legitimately unlocked his two-year-old iPhone 3G by taking advantage of what appears to be a European loophole.

He simply paid off a two-year contract with his carrier, Sonera. The Finland-based firm then forwarded the request to Apple and the next time Farshi synched with iTunes he was prompted to install an official carrier update.

“When upgrading to the iPhone 3GS, those same customers are given the option to pay off the remainder of their original 3G contract. Paying off the contract, and thus completing the two years prematurely, entitles the customer to have their iPhone 3G unlocked,” he wrote.

An official message popped up confirming that his “iPhone had been officially unlocked”.

Farshi described Sonera, which is the exclusive iPhone distributor in Finland, as a “less-repugnant version of AT&T”, before adding that the telco had “turned out to be a somewhat benevolent carrier”.

He claimed that “going the legit route was a much more painless process than using a proxy SIM or the Dev Team’s unofficial unlock”.

According to Farshi the unlock is permanent, allowing him to keep updating the iPhone’s OS, as well as being able to use any carrier SIM in the device.

Apple and Sonera could not immediately be reached for comment at time of writing. ®