question about letter of demand

What is the name of your state? Mass


I have a question about the person who was using my formmail script.
If I send a letter of demand to them for payment of the service they used (bandwidth... storage space... processer power etc)
that includes the following type of info, wont it be like blackmail?

Like this:

when you used my server without permission, you boke the law
(blah blah unauthorized use of a computer system). I am offering to retroactivly grant your preivious use of that computer system and therefore assisting you in removing the crime you committed if you pay X


Is that gonna get me in trouble?
I mean, civil suits are one thing, but this is a crimninal case on one level or the other...

How is that blackmail? Just send them a letter charging them for the past useage of the service they used and take it from there.