Just go to your telephone company web site and BLOCK the offending number, so it will not be able to come thru. If you do not know how, call their customer support!
But that's nothing permanent, because those Caller ID spoofers use a number for one day or so, then start to use some other number. The numbers they use are abandoned numbers, not yet reassigned by the telephone companies.
From Wikipedia:
Caller ID spoofing is the practice of causing the telephone network to display a number on the recipient's Caller ID display which is not that of the actual originating station. The term is commonly used to describe situations in which the motivation is considered malicious by the speaker or writer. Just as e-mail spoofing can make it appear that a message came from any e-mail address the sender chooses, Caller ID spoofing can make a call appear to have come from any phone number the caller wishes. Because of the high trust people tend to have in the Caller ID system, spoofing can call the system's value into question.
It is amazing that such a crooked practice is allowed to go on!
Where are the feds when I need them????? I wrote to my US Rep...no response!
Bottom line: IGNORE IT and never give the other side ANY information. PERIOD!