GX10 on O2 - UK

[TheAnnihilator]

my GX10 is unlocked and i got tired of vodafone being so expensive, so i changed to my O2 - UK sim, all is fine, except i have to store every number in the phone memory, as the phone displays "Cannot Write To Phonebook" followed by "SIM Card Error" everytime i try to modify a number in the SIM Card, if i press OK at the second error, it returns to the phonebook view...

any ideas?