From VoiceMailTel Wiki
The VoiceMailTel SIP Android Softphone is Android Compatible Mobile SIP client based on SipDroid.
- Notice: The current version of the application works perfectly and has been thoroughly tested by VoiceMailTel. You can download it directly from the Android Market.
Step 1 After installation click on the Settings icon.
Step 2 Please enter your information the fields. Use your own display name, username (your virtual number) and password.
Step 3 Make calls!