For Samsung/ Android Goto Settings->Connection->Mobile Networks->Network Mode sim 1/2,then u can change it to ur preferable network mode ie(2G,3G,4G lite...)

All phones may not have this feature, if there exists: Setting >>mobile networks >> preferred network types>>4G

Mejemeriya tele hedeh sim kardhn wede 4g keyer gn sim wede 4g yemtkeyrew beth addis abeba kehone new lela bota ayseram 4g network

First you need to have 4G Sim card