I am also using Voxalot to make sip uri calls, in my case from Betamax to Betamax.
Later on today I will make a sip uri call and will let you know if I got charged for it.
I am having a lot of audio problems (hum) the last few months with sip uri calls. Are you having this too?
See my topic over here:
http://forum.voxalot.com/voxalot-sup...softphone.html