Here is a list of awesome ways to prank someone’s phone. Some may not work in your country, but I have provided a few great ways.

http://www.hoaxcall.com/ – Prank call your friends using automated voices.

SMS Bomber – https://code.google.com/p/sms-bomber/

SMS bomber that allows multiple untraceable numbers, and random predefined messages – https://code.google.com/p/sms-bomber/

Hitleap.com will allow you to give more textbombs my giving your clamtxt.com referral code views.

Creepy sound board: http://www.jackulator.com/

List of soundboards: http://www.soundboards.com/

Line2 – http://www.line2.com/home/ This will allow you to use a new number for calling and texting. You can scare and fool your friends.
Free coupon code for a month: 104 74 8211

Hushed, get a free phone number for text and call pranking that no one will reconize! https://play.google.com/store/apps/details?id=com.hushed.release&hl=en
Use coupon code: WSCJ60QZZ1 for free credit.