I am looking into buying a used UK Network locked iphone 4 for JB and unlock. I understand there no hacktivate available for the Iphone 4. Can I activate the phone by using an old sim card from the same network provider or do I must use the orginal sim card that was provided. Also in the US, I heared you need the last 4 digits (I still dont know what is it?) and zip code to complete the activation process, is this the same for the UK model too?