Harassing Messages That Aren't Even Meant For Me

I am constantly receiving threatening sms's warning legal action against someone else's name who's clearly used my cell phone number for all his accounts. I have called Nudebt probably around 15 times now, and each time they guarantee me they will remove my number and will 'escalate' the issue. It has been months and I am still receiving these messages. I'm worried this man's debt is going to reflect against my name due to FICA. Can someone PLEASE sort this out!