QwertyWEB

                      Its now very easy to make call to twitter users . It works on idea to provide a platform where twitter users can call and talk or even leave a voice message to each other by avoiding the sharing of private telephone numbers. To access the received voice-mail all you need is to simply sign-in to Twit2Tel, that allows Twit2Tel to link  the Twitter user-name to the voice-mail account and apart from this a call feature of Twit2Tel allows you to make a free user-to-user calls for 4 minutes.

Go to twit2tel.com .

Just sign-in to twit2tel where you’ll be asked to authorize your twitter account.
Once you are done Click on the “Create a free account” button
Then go to “settings” and provide your telephone that you want to linked up to your Twitter username and click update next to the number. .

Example: tweet : @twit2tel call .



Check this tutorial ; 


Twit2Tel Now Offers Free Calls to More Than 200 Countries in: North America, South America, Europe, Asia, Africa, and Oceania
Link : http://twit2tel.com

If you have Jajah account , then also you can make free calls to any twitterer , check this post