Does anyone know if there's a device or whatever that can be placed on a telephone line that will "unblock" a PRIVATE CALLER id on the caller id?

I've been getting phone calls where they sit and listen and say nothing. I have a feeling I know who it is, but I have no proof. My home phone is used to take orders for my cake business, and sometimes I will get orders from numbers that show up as PRIVATE, but then they give me their number anyway later.

I don't want to change my number--there are too many business cards out there with it on there.

I'd pay good money for a "spy device" or whatever, though.

-m-