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Just found out that the way to fix this is to make the iPhone and/or the Tesla forget each other: on the iPhone, select Bluetooth and the device, then Forget this Device; on the Tesla, select Phone from the media selection, then Add a device, select the iPhone and Forget this Device. Then re-pair the iPhone to the Tesla. The iPhone will ask you if you want to export contacts to the Tesla. After I did this, then I opened the Phone app on the Tesla (^ from the bottom menu, then Phone; it then initiated reading my contacts.