Why does my iPhone 12 go from 5G to LTE?

iPhone 13 models, iPhone 12 models, and iPhone SE (3rd generation) work with the 5G cellular networks of certain carriers . Learn how to use 5G cellular service.17 Mar 2022

In a nutshell, because 5G uses a different spectrum than 4G LTE , it can deliver stronger and faster connections, higher capacity for traffic, as well as latency as low as 1ms.

Apple even says it takes into account your data plan: The default settings for 5G on iPhone are optimized for battery life and data usage based on your data plan. … However, inside the cellular settings, you can choose to turn 5G on/off on iPhone 12 manually to optimize for speed or battery life.