hi i got a k750i 2 weeks ago which was locked, however when i phoned tesco mobile customer services they said that if i have topped up at least £30 on any tesco mobile sim card thyey would unlock it for free. my dad has a tesco mobile sim card so they let me unlock it plus they gave that sim card 75mins free any network per month for three months.
in the end worked out quite well...
hish