Below is what I did to get a successful registration with voipfone. I have made an out-going call but not tried an incoming one.
Info has been taken from voipfone's website and adapted I hope this works for you.
{On the phone go to, Menu, Tools, Settings, Connection, SIP Settings
then Options and Add New. Then select Use Default Profile.
Now change just the following settings in the profile leaving all others as default:
Profile Name: *your provider*
Public Username: *your username@your provider's ip address*
Proxy Server:
Proxy server address: *your provider's ip address*
Realm: asterisk (type the word in, don't use the '*' symbol)
Username: xxxxxx
Password: xxxxxx
Allow loose routing: Yes
Transport Type: UDP *I used auto*
Port: 5060
Register Server:
Proxy server address: *your provider's ip address*
Realm: asterisk
Username: xxxxx
Password: xxxxx
Allow loose routing: Yes
Transport Type: UDP *I used auto*
Port: 5060
Now we need to link this profile to the connection.
On the phone go to, Menu, Tools, Settings, Connection. Internet Tel. Settings
From the list choose the SIP URI.
Next select Name from the menu then type the name into the field. OK it.
After entering name select SIP Profiles now choose from the list. OK.
We now have to activate the connection with .
Menu, Connect, Internet Tel. Registration Status, you should see the profile with the status Not Registered. Press Ok and if everything is correct your phone will register with us.
To make a call
From the standby screen dial the required number then press Options, Call, Internet Call.
Your call should now connect.}