Question: 2g how to change 4g?
Answer: Select Apps.
Scroll to and select Settings.
Select More...
Select Mobile networks.
Select Preferred network type.
Select 2G only / GSM only to enable 2G.
Select 3G/2G auto / GSM/WCDMA (preffered) to enable 3G.
Select 4G/3G/2G auto / LTE/WCDMA/GSM auto to enable 4G.