Phone [Q] Andoird 4.2.2 Network Mode" is Disabled


I am Uresh and have Lenevo A850 with android 4.2.2 Installed.
I have issue with data connecion.I have 3g plan in my operator.
When i start internet it automatically take GSM mode.
I want to change it to CDMA/WCDMA mode.

Settings - > All Settings -> More ... -> Mobile Networks -> " Network Mode" is Disabled.

Please advice something or solution ,what to do for that ?

3G Network: WCDMA 900/2100MHz (AP/EAST/MEA), 850/1900MHz (LA)
2G Network: GSM 900/1800/1900MHz (AP/EAST/MEA), 850/1800/1900MHz (LA)
Speed: HSPA+ 21Mbps (DL) / 5.76Mbps (UL)/ EDGE