Poor call quality can be the caused by several factors such as the type of internet connection you have or the amount of bandwidth available or the distance between you and the VoIP server.
When there is no sound, or only one way sound it can mean the audio is being blocked by closed ports on your router or firewall. You should try running the built-in 'Network Setup Wizard' and if that doesn't help, please visit your router or firewall manufacturer's website for details on how to set-up "port forwarding" to open ports Axon uses to make phone calls.