Okay skippy this is an easy to do thing. 1st you need to make a fake G-Mail account. The G-Mail address will show up in the messages, so don't be a dummy and use your regular account unless you want them to know who bombed them. If that is the case then you have declared war.
Start iPwN and follow the steps.
When you are asked for the g-mail account input the whole thing including the .com and don't forget your password for the fake gmail account.
When it comes to the part for phone number use the area code also but not the 1+.
When it asks for the carrier that's your targets carrier silly not yours.
When it asks the number to send, send no more than 250. This should lockup their phone and/or send it into an apoplectic fit.
25 text bombs is annoying. 50 - 75 is brutal. 100 is torture. 250 is just plain merciless. Have fun.
Play safe, play smart, but don't play fair.

This is the tut i wrote for iHMi.