Identity theft. If you get a call from this number, you have already been targeted. Subject matter of these calls are custom tailored to each individual target. The caller is looking for specific information, I have heard the term "Tid-Bit" used to describe personal details gathered this way. Even if you do not answer the phone, that fact is a "Tid-Bit", or, if your phone is off, that still is a detail that identity thieves can use. Be careful.