Issue found for my device.

1-我在我的運營商4G服務,但我的移動網絡不改變網絡模式為LTE / WCDMA,它始終在GSM / WCDMA / LTE。
(ATT三星Galaxy S III SGH I747)為我的設備MK71.2解決這些問題.

English Translation.
I have an issue for my device.
1- I am in my operator 4G services, but my mobile network does not change the network mode to LTE/WCDMA, it always on GSM/WCDMA/LTE.
2- When i looking for another network in search network setting, after 3, 4 minute while search they gives me message that "network searching error"
kindly fix these problem for my Device MK71.2 for D2ATT as known (ATT Samsung Galaxy S III SGH I747)