most times they can only confirm any info they are provided ..like the person calling the Company would have to tell them what they know and the company would tell them only certain items ..they can not volunteer your info…and it can only pertain to company stuff like are you still employed and what your job title is ..start date ..things like that ..anything more they would need your permission
but the truth is it would depend on the person who answered the phone ..if they are train right you are ok if not they will tell them anything