3 Big Green Candles, page-134

yes, the quality is better because it only travels the shortest possible distance over the internet before jumping in to the global phone network, unlike Skype and viber which go through every router between here and there.

..."We can charge less for calls because we do not need to have a contract with every mobile network in the world. We use the public internet for short VoiP hops, which is free, and then we use the PSTN which is so competitive that rates are very low. World Phone allows you to use a local number on your iPhone, even when you have a roaming SIM card installed. This is is a significant benefit. Instead of allowing your PBX to forward a call to your roaming mobile, Work Phone sends calls over the PSTN from your PBX. This saves your company a lot of money and you can make high quality calls "