The best letter to send to payday companies

My girlfriend got caught up in the payday loan nightmare and I'm trying to help her and give her all the information I can. I never sent a revoke letter to the companies saying they are not allowed to debit my account anymore. She wants to do the right thing and send letters. She told me that after the 3 she took out she will never do this again. I told her good...I definitely learned my lesson thats for sure.

Does anyone know of the best and efficient letter of revoke that I can give her?

Thanks so much.....