Do a search in the internet and you will get plenty of letters in this issue.
Have you checked the
letters section in this website? There are many letters specifically for the purpose of creditors, credit bureaus, CA's etc.
You can also go through the
books section for some good letters.
All payday loan companies need to be licensed in your state before lending. Besides, you must pay within the permissible interest rates and fees as per your state laws. Check this link for payday loan regulations in your state.
http://hffo.cuna.org/download/1168.pdf?&sub_id=14490