Sub-contractor incorporating part of our name

We are a supplier that sub the installations out to a sub contractor. Recently the sub has used our name to incorporate and added one word to it.For example; our name is Global Systems, Inc, the sub incorporated his name Global Systems Installations, Inc.We are now expanding to handle installations and service within our company. We don't have a contract with the sub, we are sinply not going to use him. He will have our name and try to be our competitor. Is this illegal. Does he have to give up the name or do we have to go to court over it and let a judge decide.Really appreciate some advice.

This would seem to be a deceptive business practice likely to cause confusion among the customers and taking unfair advantage of your name.

Your rights depend on the state you are in and whether or not you have a registered trademark. But from my experience it will take at least a threatening letter from a lawyer to get them to stop and change their name.