How can I call a phone number using the Sip capabilities?

All examples I've seen require a SipProfile of the person I'm calling. In this case I'm not making a voip-to-voip call, but rather a voip-to-landline call.

Basically I want to mimic what the default Caller application does, you set up a Sip account and just call the person to his/her phone number.

Thanks in advance.

I managed to get it working by forming the address like this: xxxxxx@server.com where xxxxxx is the phone number to call. I don't know if it is the standard way, but it worked with my current VoIP provider (Plivo) since it creates endpoints dynamically.