To add i2voip service into the Nimbuzz select setting from the options menu.
Choose SIP/SIP Providers from the list.
Now select Others from the list of VOIP providers.
Enter your user id and password as shown in image.For example yourid is 35469 the enter "firstname.lastname@example.org" then your passwor in the password column followed by the Proxy server as "sip.i2voip.com". Now save.
Now go to home menu and choose Dial number.
Now dialer moded to Nimbuzz call. It must be set to our sip account.
Choose voip provider setting from the options menu. Then Select SIP from the list. Now u can star calling.