As far as the iPhone 4 I do not have any more information than what is on the site you referrenced in your first post but I did look into deleting a paired phone from your bluetooth system and this is what the manual says:
Deleting a Paired Phone
1. Press and hold b g for two seconds. The systemresponds with “Ready” followed by a tone.
2. Say “Bluetooth”. The system responds with“Bluetooth ready” followed by a tone.
3. Say “Delete”. The system asks which phone todelete followed by a tone.
4. Say the name of the phone to be deleted. If the
phone name is unknown, use the “List” command
for a list of all paired phones. The system responds
with “Would you like to delete? Yes or No” followed by a tone
5. Say “Yes” to delete the phone. The system responds with “OK, deleting”.
If going through these steps does not help with the issue there could be a problem with the system itself and I would suggest having the vehicle looked at by your dealership. I hope this information helps you.