Proper configuration of Siphon (Iphone VoIP client) so that you can use it with VoiopCheap.com provider should look like:
Account Username: 00XXXXXXXXXXX Password: ********** Server: sip.voipcheap.com Advanced settings: Reg.Timeout: 1800 Proxy Server: sip.voipcheap.com Enable NAT: Off Auth. Username: VoipCheapUSERNAME Contact: