Yeah, I'm very new to sip/voip as well.
I did watch the LAS AsteriskNow setup video a couple of days ago as I subscribe to their podcasts.
Anyway, I contacted localphone.com, my voip provider and he told me I can only make free sip to sip calls to other localphone.com users. Also, If I want to make and receive calls to/from PSTN, mobile phones and etc, I will need a DID number and pay usually fractions of a penny per minute to call those devices.
Thanks for the reply