So I, like many others out there, have Sprint. And I also have the pick 3 numbers on my account. And now I finally got my Google Voice Number. What does this have to do with anything? Let me explain. With a “pick X amount of numbers that you have unlimited calling to” and Google Voice, you have all the ingredients for free incoming and outgoing calls without using a single minute.
The guide below will show you how.

1) First thing to do is register with Google voice. Get a phone number with whatever number you want to give out. This will be your “new cell phone” number. When you register with GV, you will be asked to add a phone to your account. Add you cell phone and finish setting it all up on their website. (You probably want to import all your contacts into GV so callers don’t need to announce their names).

2) Now call up sprint and give them you GV number and tell them that you want that as one of your free numbers.

How does this work you ask? Well, the caller calls your GV number and Google calls your cell. It shows up on your cell bill as your GV number calling. And that number is free to call you!

Now for the outgoing…

Method Number 1: (Paid) Get MagiCall HERE!. Install and start program. Copy the attached file to /device/my documents/magicall (thanks Solange82200) overwriting MG2RULE. Reopen the program GUI. It will ask if you want to load the new rules. Click Yes. Modify the rule called Google Voice with your info. (your phone number, leave the commas and then your pin. Leave the rest alone).
Set up whatever rules you want and enjoy free outgoing calls.

Please note that you should not set up any new rules before the import as all your old rules will be overwritten.
Thanks goes to Biker1 (and sorry that you lost your rules).
Thank his helpful post here!

NOTE: If you go from using 800 minutes a month to 0 sprint might notice. use this to not go over your minutes...
Maybe only place outgoing only or whatever.

You MAY send me PM'S for help with setiing up MagiCall but I MAY NOT be able to answer all your questions.

Oh....don't forget to unrar the file. Rared b/c of forum rules...