You could talk to a tort lawyer about the possibility of filing for intentional interference with a business relationship, if the elements for that tort exist. I am not aware of a criminal statute that prohibits using people's texts without their permission. If there is such a statute, you would have to file a complaint/report with the police and if they found sufficient evidence to submit it to the state attorney, then the state attorney would decide whether or not to prosecute.
***Please be sure to mark if you find the answer "helpful" or a "best" answer. Thank you! I hope this helps. ******