Try the following: Pennytel User name 888917XXXX@sip.pennytel.com (this uses your Pennytel number) Password zXXXXXX3 (Pennytel supply you with a password when you join) Then go to Advanced settings Use for telephone numbers Make sure this box is checked User name 888917XXXX (Your Pennytel number) Transport Auto Outbound proxy sip.pennytel.com Port 5060 Discover public addresses Make sure this box IS checked Loose routing Make sure this box is NOT checked Keep-alive mechanism Auto Keep-alive period Auto Auto detect STUN Make sure this box IS checked