If you haven't already tried it, You could try the "logging Off" Procedure from the handbook
Logging Off
You can log off your mobile phone if you no longer wish to operate it from the vehicle. This process logs off all mobile phones that have been logged on.
1. Hold the button above the storage compartment pressed, then after about 3 seconds turn the ignition key to position 1 and release it after approximately a further 3 seconds. "BLUETOOTH PAIRING" appears on the display or monitor.
2. Press the button again for approx. 10 seconds until you hear a triple acoustic signal. "PAIRED DEVICES DELETED" appears on the display or monitor.
3. To conclude the logging-off process, turn the ignition key to position 0.
All mobile phones that were originally logged on are now logged off.