Just the other day a got a call from my new dentist calling from another line. I added that one to my contacts and in the ID I added "line 2" to his name. If a number is not on my ID, it can go to voice mail. If it's that important they will leave a message. My niece lives near D.C. Of course I have her on caller ID. Anything else goes to voice mail. Anytime I call a number, I put it into my contacts. When they call, even if I've never spoken with them before and always put a word or two like "car CL" telling me about a car on Craigslist or such. You can always go back and edit.