Use APKPure App
Get 4G LTE Locker 2020 (DUAL SIM) old version APK for Android
This app will help You to change or lock network to 4G/3G/2G
In most of android phones does not have 4g only mode.
This app will helps to lock any band and stay on that mode.
This app don't have any special features .This app will help you to access android hidden settings.Read help section if you are facing any problem