You do the following (well, this works for me):

1) Press and hold the button under the armrest for 3 seconds.
2) Turn the key to Pos2
3) You should see "bluetooth pairing" come up on the instrument panel.
4) Release the button
5) Immediately press the button again and hold for 10 seconds, or until the system beeps (usually loudly) 3 times. You will see Devices Deleted. It will stay in Pairing mode, so just pair the new phone.