If the person on the US is making a VOIP call to the A800, and the a800 goes VOIP to the A to Z provider, it is not that easy.
Now, if the person with the phone want to go VOIP to South Africa, go PSTN from there to India, that is everyday deal.
Again, VOIp, quintum and PSTN the rest of the way, no trouble.
VOIP, QUintum , and back out on VOIP to another provider, not easy.
You need a softswitch for that.
If you need information about how to setup a A800 for “hopp-off”, or pass-thru, I will be gald to do it for you.