Ya friends you can call someone on his cell phone with a International number with help of Internet and your cell phone and talk to him with your cell phone only.Also its free too for limited period(check NOTE at the end of this post). It's not a prank .Instead now prank someone with this cool trick. There's a site www.mobivox.com
Note:Its tested by me and its working!
1>>Visit it and Register yourself(with your REAL mobile number).
2>>Confirm your email.
3>>Login into your account.
4>>Click on "Direct webcall"
5>>Choose Country and the cell number of your friend(Your number will NOT be shown on the receiver's phone) and click on Call Now!. Then you will Receive a call from a unknown number. Pick it up and then they will call your friend's number.
After Clicking Call Now a call will come on your cell phone(The number you filled while registering yourself on www.mobivox.com) from a International number. Pick it up. And then the number you filled(in the above image) will get a call from that number. Talk and Enjoy!
Note: Drawback of this website is that it gives you only 5 min to use it for free(As shown in the above image with green arrow)After 5 min your call will get disconnect. BUT BUT BUT IF you will register with a new email id and same number then it will work again. :) :) :)
Use this site only for Prank purposes. If you abused someone badly then he could complain about you and you will be behind the bars. Do it at your own Risk.
Do comment if some problem persists.