Allied Interstate Collections-NOT THE PERSON TRYING TO REACH

I work for a california county child support office and I have been receiving phone calls from this collection agency and previous ones for aproximately 4 years. This is over a phone bill that is for someone I do not know and gave my office number as their contact number. I have explained several times and I guess they think I am lying. I am not the person they are trying to reach and am very upset as I have perfect credit and do not deserve the harrassing phone calls. I have requested that they stop yet they do not. The number they leave to call back is 1-866-221-3230.