Android question-> free calls

[kramerjm-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org (James Kramer)]

Two questions about Android:

I have an android phone with a good data plan but rather costly call
minutes.  What is the best way to make free calls using the data
network?  I have a google voice account.  Is there an apt that will
ring my phone when I receive data based calls?

 I also do not understand how android controls processes.  It does not
seem like there is a way to kill an apt.  I have read that there are
apts available to kill processes but that it is unnecessary because
android has a way to load balance processes so that it is really not
necessary to kill the process.  Is this true?

Thanks for the advice.
Jay