Just get a carrier that does no monthly charge, with a 10¢ a minute rate.
I did, when I had MCI it was a $4.95 a month just to be a customer. I eventually went with AT&T for the 10 cents a minute no monthly charge. I was burned by a roommate that ran up a $3700 phone sex bill on my long distance bill once. (The short story is here in a previous post I made about small claims court) So to be able to totally disallow LD calls from my number would be wise in some cases. And $5 a month would have been much cheaper!