As per the rumours the new iPhone 4G HD seems to be having a micro card slot, Apple recently released iPad with micro Sim card slot, so don’t be surprised if you see a micro sim card slot in the new upcoming 4th generation iPhone.
The micro-sim is an updated and miniaturized alternative to the standard mini sim card. It is smaller to the mini-sim in size but circuit area is same as shown in the image below.
In order to convert a mini sim card to a macro sim card, you just need a plastic cutter to cut the extra edge of your old AT & T mini sim card to convert it into macro sim card. This method may work or may not work to, so better try it with your old sim card which is not in use, and wait for the apple to ship their iPad 3G models or new iPhone 4G HD
[ Thanks To Sizlopedia ]