Apple sold two different models iPhone 7 and iPhone 7 Plus phones in the USA. You may use these phones with Straight Talk Wireless’ BYOP SIM card and plan

For the iPhone 7 Plus, Apple sold the A1661 model for customers using Verizon or Sprint and A1784 model for customers using AT&T or T-Mobile. The A1661 model was also offered as the SIM-free and unlocked phone that was compatible with all carriers.

When you sign up for Straight Talk’s BYOP plan, you have a choice to use their AT&T, Verizon, or T-Mobile towers. Choose the network that is compatible with your phone and the towers that best have coverage where you use your phone.

If your iPhone is unlocked it will work with either the Straight Talk AT&T SIM or the Straight Talk T-Mobile SIM card. To find out if your iPhone 7 is compatible with Straight Talk’s Verizon network, check the phone’s MEID / IMEI number directly on Straight Talk. Note the MEID / IMEI is different for every phone, so you need to check the exact number for your phone. You can check here Straight Talk Verizon Compatibility