Hollis Johnson You can check to see if your iPhone is unlocked in Settings or by checking the IMEI and serial number online. You can also test your phone by swapping SIM cards with another phone that has a plan with a different carrier. If your iPhone is unlocked, you can switch wireless carriers and use a different carrier's SIM card in it. In the early days of smartphones, pretty much the only way to get one was by purchasing it through a wireless carrier or in conjunction with a wireless plan from a specific carrier.