With withheld numbers, I don't even bother to answer them. As StrawB said, there is just too much hassle involved, the principle point of with holding the number starts the whole relationship off in a negative way. The other person on the other side is taking no risk and is hoping to get all the rewards, so I refuse to play ball. I had one guy call and I answered thinking it was my girlfriend I had just spoke to, when I asked him to call back with his number showing, he replied-"I don't do that, I don't give out my number." You can not imagine how this got my back up! I replied, "Then we have a problem, I AM NOT GIVING YOU ANY INFO, until you call back with your number showing, good day!" And hung up. Cheeky sod.