One way would be to get TrapCall on your phone.It is a free service that unblocks private callers.
Secondly you can bust a private caller by forwarding unanswered calls to a toll-free number instead of voicemail deposit. Then don't answer private calls. Caller ID cannot be blocked to toll-free numbers.
You can use the toll-free provider's voicemail or forward the call to another line from there.
The toll-free provider you can use is Kall8 which immediately sends an email with the caller's name (if available) and number. You can have this sent to your phone. This provider charges I believe still $2 a month and 6.9 cents a minute.