W715 Video Call doesn't work

[#1]

I have W715 unlocked from Vodafone.

Using it in US with AT&T.

Trying to use video call function, but keep saying "Video Call Failed".

Do I have to change any setting in oder to use video call?

Someone help me!!!

[Dr_Chris]

Do both you and the person you are trying to video call have a 3G signal?

[#3]

Yes, 3G signal + WiFi at same time.

[Dr_Chris]

Switch Wi-Fi off (both you and the person you are calling) and try again over 3G.