SamsungI9300 Galaxy S IIINetworkChange networkmode
Your Samsung Galaxy S III automatically joins the fastest data connection available. In some situations, you may want to switch to 2G, 3G or 4G. To manually select the connection type, follow these steps.
Note: Switching down to either 2G or 3G respectively when in either a 2G only or 3G only coverage area will help save battery life.
To start using a faster internet connection again, switch back to a higher network mode.
Choose More settings.
Choose Mobile networks.
Choose Network mode.
Tick GSM only.
The Samsung Galaxy S III has now been configured to only use 2G networks.