Dual SIM Adapter
The Dual SIM Adapter is available for different versions of the iPhone. I only picked this one out because of the amount of customer reviews. You can find the right adapter for the phone you have through the following link: Browse All Dual SIM Adapter options here
The Dual SIM Adapter allows you to use two different SIM cards as you need them while protecting the unused one. These are for the Dual SIM smartphones. The adapter has 2 different SIM cards connected to each end. The one shown here is the Dualsim Adapter for iPhone 4. See more product descriptions, specs, and images through the following link: Read More About Them or Buy Them Here!
Dual SIM Adapter Pros:
Makes it much easier to use your dual SIM smartphone during travel situations, and less likely to lose the extra SIM cards. Many versions to choose from for your specific phone.
Dual SIM Adapter Cons:
The reviews on this exact version of the dual SIM adapter is actually pretty bad. You can read the reviews yourself and be your own judge on this one. Some iPhones require a restart upon swapping cards.
More Dual SIM Adapter options
This option here is the Hypercard 3G dual sim adapter. Combines two Sims all in one Sim card. Use two sims in one phone. Click the image to read more specifications and purchasing details about this one or browse through a whole bunch of others by clicking the image.
If dual sim is not enough SIM for you, then you could also consider this option shown here. This is a triple SIM card. It is a Socblue dualism triple SIM online bluetooth adapter for Android and IOS. You can have three active numbers controlled by your android phone. You can add phone functions to tablets, and have three numbers running at the same time. Read a lot more details about this and other triple SIM adapter options by clicking the image you see here. There, you will also find customer feedback reviews by people have already purchased and used these.