automated call, automated message claiming to be debt collector requesting call back

Its a legitimate collection agency, they work for companies like Comcast.  I say legit, but not ethical.  They harass constantly, even after asking them to stop calling, which is illegal.

got calls from 404-602-9683, 404-602-9703, 404-602-9696. Thing is, they are calling a work issued cell phone. I don't give the # out to anyone, so I know the calls are not for me. I'd been getting calls from other collection agencies at the same cell #, so I wonder if the cell # was issued to someone who had these agencies looking for him.