Yes. If you unlock a network locked iPhone, you then use any international GSM SIM card with it. you must be having no problem in it. The safest and easiest way to unlock an iPhone is to unlock using remote unlocking service. You can get the remote unlocking service for an iPhone from Mobile-Unlocker.com at affordable cost with easy unlocking guide. This is a permanent unlocking method and doesn't require a jailbreak too. Good luck mate.