How Do I Activate 3G Only On Samsung Galaxy A5(2015) I use Samsung Galaxy A5 (2015) and I have just upgraded the firmware to Android 6.0 (Marshmallow). The phone supports 3G but the option to set it is LTE/3G/2G (auto connect) on Network mode.

How do I get the phone to use 3G only?
Try to call ##4636## then select Phone/Tablet Information, scroll below and you saw Spinner, select 3G/WCDMA only

Or

Goto Settings > Cellular/Mobile Network > Your 3G SIM > Network (3G only)