if you don't have google voice (yet) this is still a good idea...
call account services at sprint. tell them a sprint store representative (or whoever) told you there was a "3 numbers" feature that you could get on your phone. it's like the t-mobile fav-5 or whatever. they are trying to get away from it, and only use it for customers who are thinking about defecting. however, they should honor it if you said a sprint employee told you about it.
i have 3 lines on my plan, and was able to get 3numbers on each line. my wife has her mom, sister and best friend. my friend and i both have our google voice numbers on it. if you have google voice, and use the dkGoogleVoice app, you will never use any anytime minutes for ANYONE that you call!!!
they might play hard, and say they no longer offer it, but tell them they should honor it since a sprint employee told you about it.
hope this helps!!!
***EDIT***
just did this an hour ago, so i know it's legit and still possible.
