Linphone is probably the only multiplatform SIP VoIP client available not only for the main platforms (Linux, Iphone, Android/2.0, Windows and MacOS) but also for BlackBerry and Windows Phone.
The following configuration sample is provided for the Windows version; however, the other versions should be very similar. You may follow this guide below or via the screenshot album.
Start Linphone softphone.
While it may be possible to set up a new account via a wizard, we have found that way to be buggy in the version we tested and as such suggest you avoid it.
Click on the Linphone menu and select Preferences.
Go to the settings page of Linphone. On Android it is accessible through the "menu" button, on iPhone the settings are located within the Settings application, together with all other iPhone settings.
On the Settings page click Manage SIP Accounts.
Under the Proxy accounts section, click on the Add button and complete the information corresponding to your account, as obtained from login under My Services.
When prompted for Authentication, enter again your UserID and password.
Congratulations! Your Linphone is ready for use!