I have actually talked with individuals on these lines.  They are very nice and polite and definitely ARE with the Trump volunteers.  They will tell you anything you wish to know about the Trump candidacy.  They are also very sympathetic when you ask to be taken off the list, but tell you they can't help with that request as it is special interest groups that create these robocalls and not the Trump organization itself.  Just block them if you don't want them.