Samsung Galaxy S4 on Verizon network: 3G CDMA network retirement

https://www.nextpit.com/how-to-enable-4g-on-a-samsung-galaxy-s4

https://www.helpforsmartphone.com/public/en/samsung/galaxy-s4/android-5-0/guides/24/Switch-between-3G-4G-Samsung-Galaxy-S4-Device-Guides

https://www.att.com/idpassets/images/support/pdf/Devices-Working-on-ATT-Network.pdf

https://qz.com/1550936/heres-how-much-your-old-samsung-galaxy-phone-is-worth-now/

https://www.verizon.com/support/samsung/