Installation and Configuration of native Android SIP

1.) Go to Settings and then to Call Settings and find "Accounts" settings.

2.) Under" Accounts" find SIP Accounts and click "Add Account" button.

3.) Enter the following information;
User Name: 610xxxxxxx (Instead of 610xxxxxxx account number example, use the account number assigned to you - e.g. 6105- when signed up for Mobtel service. ) Password: Enter the same password used to login to your Mobtel account
Server :

Enable "set as primary account".

Once you enable Internet Calling under Settings, you are ready to make calls using Internet Calling over Wi Fi. Calls over 3G is diasbled.