When a Tesla is unlocked and you're in the middle of a call, it's pretty eager to switch the audio from the phone over to the car. This can be frustrating when you're in the middle of a call and you are not even inside the car yet. Or when you're near the car and someone else gets in the car a similar thing happens.
Suggestion: use the seat occupancy sensor to check if the driver is in their seat. Once the seat is occupied, then switch the Bluetooth audio over to the car.