This is the ad free version of app https://play.google.com/store/apps/details?id=switchmode.lteonly.lteonlyswitch So before purchasing this app, please check whether your device support this feature.

It is common that some handset swap 4G signal to 2G or 3G because of low 4G coverage. 4G LTE Only Mode Pro allows you to lock the device only in 4G mode.