How to enable 3G network on my galaxy s??

hi to everyone..

i recently activated 3g network on my galaxy s for only video calling only..


when i turn on to data network mode on it will comes 3G network just flash out after then  H network comes out in the notification bar.

cannot stay on 3G network.(when turn on data network mode just flash 3G)after appear H

i tried to set to mobile networks>network mode> gsm/wcdma (automode).

but cannot stay 3G network. in my network operator says your mobile is activated 3G network. but in my mobile appears H network.

i had checked out in settings>phone status>mobile network type> HSDPA.

Say what to do now?????

but cannot make video calls with H network.

so what's up???