I had my iPhone unlocked in anticipation of the trip to Colombia. I figured I would just swap out my SIM chip and get a local carrier account for local use. During my research online for South American phone companies and plans, I learned that my phone would not work in Colombia at all.
My plan is with Sprint. Sprint and Verizon phones use CDMA (Code Division Multiple Access) network. What this means is in the U.S., CDMA carriers use network-based white lists to verify their subscribers. That means you can only switch phones with your carrier’s permission, and a carrier doesn’t have to accept any particular phone onto its network. It could, but typically, U.S. carriers choose not to.
Many Sprint and Verizon phones now have SIM cards, but that isn’t because of CDMA. The SIM cards are generally there for Sprint’s and Verizon’s 4G LTE networks, because the LTE standard also uses SIM cards. The phones may also have SIM slots to support foreign GSM networks as “world phones.” But those carriers still use CDMA to authenticate their phones on their own home networks.
Most of the rest of the world, including Colombia uses the GSM (Global System for Mobiles) network. It’s much easier to swap phones on GSM networks, because GSM carriers put customer information on a removable SIM card. Take the card out, put it in a different phone, and the new phone now has your number. What’s more, to be considered GSM, a carrier must accept any GSM-compliant phone. So the GSM carriers don’t have total control of the phone you’re using.
So based on this information, I bought a second phone for use locally in Medellin. I could have waited to buy it there, but electronics are more expensive in Colombia, so I ordered a cheap Windows based GSM 4LTE smartphone off Amazon for under 100 dollars. My iPhone will be used for international calls through Wi-Fi and for when I’m traveling back and forth to the US for work; which apparently will be a lot based on the latest report.