That's because jailbreaking is different to unlocking.

Jailbreaking = giving you root access to the phone.
Unlocking = removing SIM restrictions.

Yes, I know.

Turns out I had to use a particular version of [whatever the app is called]. Not hte current version, but some random old version, then upgrade to the iPad firmware (and /only/ upgrade to Ipad firmware, nothing else), and /then/ downgrade to an unlockable iPhone firmware. Took best part of 2 days to get the unlock sorted. Cocking iPhones. It's much simpler on Android.

Jailbreak and Unlock are two different terms but they are both usually confused. Jailbreaking allows a user to install third party applications, software, themes and removes the limitations that are on the apple device. In short it gives the user the root access to iOS whereas unlocking means the user can switch between network carriers.
To jailbreak visit jailbreakiphone4sim.com and for permanent unlock service use Mobileunlocksolutions.com