Sir, my sony erricson phone, flip model i think it is Z550i, is phonelocked , i was vodafone prepaid, now transfereed to psot paid, they gave new sim, which when i insert ask for for code for phone lock, i have never locked before, my old prepaid sim is still workilng oin same ph9one but for new one they ask code, i changed to another new sim post paid one but theproblem still persist, please help,vodafone poeple say i haveto change the phone.but my phone isworking on old sim then why not on new one.