I have tried both methods listed above on both a 5360 and 5330 at my desk and I can change both to SIP. Once you get to Phone Mode press *, the you see Protocol - Press *, then it says Phone Mode: Minet - * to change, 0 = SIP, # to accept, * to store changes, then * to reboot then phone. Now I have to put my phone back in Minet, all for a good cause if it helps you.