MagicJack is the answer. I have a MagicJack number that I give to pretty much everyone except family and a very few close friends. Everyone else gets the MagicJack number. If they demand my cell phone number (like more and more businesses seem to be doing), I refuse and tell them that I'm taking my business elsewhere.
On the unlikely chance that I have to call any of these people or businesses, I use the MagicJack number so that remains the only one they know about. Other than that, it rarely gets used and is not answered. The ringer's turned off except for those rare occasions when I'm expecting an important call on that number. Otherwise, everyone goes to voice mail, which I rarely check and even more rarely respond to.
My cell phone is a prepaid from Straight Talk registered to a fictitious name. I forget what it is offhand. Possibly Letitia Snipe, but I forget.
As for text messages, I rarely check them unless they're from family or friends, which I know because they have a special tone. Everyone else is silent, and I just mass delete them, unread.
Somewhat ironically, the number I rarely get calls on is my business number, which is the only one that's public. My existing clients rarely have reason to call me, new clients prefer using the contact form, and my upstream providers always get paid on time and have no reason to call me.
I think the last call I got on the business line was from D&B asking me for some information for my business credit profile, which I refused to give them. If I need a loan I go to my credit union at 9:00 a.m. and walk out with the money by 9:15, so I have no use for banks, business credit profiles, or D&B.
Rich