Since these iPhones are not locked to a carrier, users can sign up with any compatible carrier of their choice.
However, unlike iPhone 3GS, the new iPhone 4 does not support the conventional mini-SIMs. Instead, users will now have to order a new micro-SIM from their carrier.
Micro-SIM for iPhone 4 can be a problem if your carrier does not offer micro-SIM cards yet or takes a long time to process the orders.
There is however an alternate solution. The following how-to guide will take you through a step-by-step process to transform your mini-SIM into a micro-SIM. For the process, you will require a mini-SIM, a marker pen, a ruler, cutter knife and a filing tool.
Before you proceed, here are a few caveats to note. The chip on the SIM can be delicate and this procedure may permanently damage the circuitry on your mini-SIM. So do remember to proceed with caution. It is a nice idea to try the process out with a secondary SIM before carrying out the procedure on your regular SIM.
Step 1: The most important part of a SIM is the central circuit that contains information about the subscriber's ICC-ID. The first step is to measure the area around this circuitry based on the size of the micro-SIM. 12mm x 15mm is the standard dimension of a micro-SIM. You may do this with the help of a ruler and a marker pen.
Important: We would strongly recommend you to wait for your iPhone 4 so that you can confirm the size of the micro-SIM that fits iPhone 4's SIM tray before using this guide.
Step 2: The mini-SIM needs to be cut along these marked lines. But before you proceed, run a cutter knife a few times over these lines to prominently mark the sections.
Step 3: If done correctly, you may now be able to break away the plastic portion of the SIM that is not required. Alternately, use a scissor to cut along these marked lines.
Step 4: You are almost done. Use a filing tool to soften the cut edges.
The new micro-SIM for iPhone 4 is ready. You may now insert this SIM into your iPhone for use. If you are buying an unlocked iPhone 4 and are trying out this process then do not forget let us know how it works.
Note: If you're in UK, you can checkout this link to find out more details about getting the new micro-SIM from your carrier.