We have to understand that telecom business and more VOIP requires from people with good knowledge of telecom (Technical people) to attack technical issues.
How many times I have had arguments with providers that tells me, “Well I do not know why it does not works for you if I have other customers running traffic”.
VOIP with H323 is a signaling world where you can find Hundreds of parameters to make them match, there is no Plug and Play device for VOIP and most of the devices require intense troubleshooting to find that the problem is probably h245 signaling or that answer supervision has not been activated or that the one way voice problem is caused for a missconfigured router, etc.
I suggest to any entrepreneur on the VOIP business, before trying to go into this business to create a good alliance with your tech or people that will run your network because When you have problems and BELIEVE ME you will have them, you will find sense to the words TIME IS MONEY.
Regards,
Saul Bejarano