How do you unblock a number on your home phone?
Do you mean if someone called you from a private number? To see who it was?
Although you can't "unblock" the callers number, your telephone company has a record of the call. Contact them. If you received a threat, they will give the local police the number for prosecution.
what if its not a threat you just want to know which of your friends did it with out contacting the police??