I remember the good ole days when I only had one cell phone; now I have three. One for business with a number that is given to many, one for business that is available to only a few select people in the office, and one for personal use with a number that only family and close friends can have.
I have a dual SIM card phone; it works good for the purpose you described. One SIM for business, one for friends.
It sounds like you could make use of this app: http://www.line2.com/home/
I do the same thing by using a single phone, with two “virtual” numbers that forward to it. The caller ID is set up to show which number was dialled so I know if the call is business or personal.
Don’t you have a fourth phone, for sexting? :)