A sim swap will be done, it's best to keep the S3 off until you loose service on your regular handset. If its the green network this usually takes 2 working days... I had the same problem when I got my iPhone 5
option 2 - call whichever mobile company's help line.. 600 for digicel tell them u wanna transfer a number to a new SIM
if its corporate u need to get whoever deals with phones at your company to do it cause there's usually a password or q and a that needs to be answered