Web callback, connected, but no sound

[singingwolf]

I have set up two voipstunt accounts with voxalot, using one to call my own cell phone, and the other to call my landline. buy clicking the call button, my cell ring first and i pick it up, then my landline rings, I also pick up, both connected. But the problem is that I can hear nothing from both of the phones, absolutely silence, though connected.
I tried to set the preferred codec to ulaw only for both accounts, things are the same. then I set both to G729, no change.
I am in Singapore.