How can you find out who is harassing you on your cell phone when they are also calling from a cell?

you can't cell phone companies have privacy laws they have to follow. If the harassing was considered dangerous the police can get involved to get the name of the person.Your best and easiest solution is to just change your cell phone number and be cautious of who you give your new number to.

ANSWER but this isn't entirely impossible. if you give your number to your friend and then your friend gives it to another person who says they only have good intentions, your number can spread like wildfire because the other person may use it for "cruel intentions".