How to stop my phone from unlocking during a blutooth call?

[blue-eye-boy]

I have a Sony Xperia Z3 compact, running andriod version 5.1.1.
Every single time i used it for through my car bluetooth, it wakes and unlocks. It really frustrating, as its always in my pocket, and then I have to remove it while driving to lock it again, missing the whole safety point with bluetooth.
I googled a lot, but couldnt find a solution, password unlock also wont work, because my phone unlocks anyway with bleutooth.

Any suggestions how I can overcome this?

Thanks

 

[dj_jyno]

That's the way it's designed, I'm afraid. Technically the proximity sensor should keep the screen off if it's in your pocket.