United Pre-Litigation calling me in Houston

I have been receiving calls repeatedly from this company at my job and on my cell. After telling them to stop calling they refuse to stop. Some way they have my aunt's cell number and has called her as well!!!! They are threatening to show up at my job, which I know they cannot do, but asking for my boss is unacceptable! I have no problem with them calling my cell, but work is off limits. Those scare tactics do not work on me, but it's totally annoying to constantly receive calls at work. They also are saying they will file criminal charges, which again I know they cannot do. Someone needs to investigate them asap. The guy that keeps calling me his name is Ed Frankel.