Never ever answer your phone, cell or landline, when the caller # or caller ID shown says it is you.
Such calls are made using VOIP - voice over internet protocol - the kind of calls you can make with applications like Skype and Magic Jack devices. Experienced techies using VOIP methods are EASILY able to make it so the caller sees the incoming call as from whatever number in the world the person making the call wants them to see.
There is no doubt that even many of the political and advertising robo calls you get do not really come from the area codes and phone numbers those calls are identified with. Even more and more of those outfits are trying to mask where they are really located.
I pick up and pretend that the call must be me calling myself from the future. Ask the Indian at the other end where and when we will meet, do we work together, etc. They're baffled for quite some time.