Bluetooth Calling issue

Hi Everyone.

I have problems to call over Bluetooth. When i am connected to Bluetooth Headset or my car, i can hear Music. No Problem.
But when I want to call someone or been called. The sound goes only over the smartphone speaker. Settings on screen says bluetooth. But no one can hear me and i cant hear the other side.

I am on Version:

So. Bluetooth connected. No Sound while Calling. But can hear it on small Phone Speaker. Different Bluetooth Devices tested. switched between loud speaker, small speaker and bluetooth while calling. Bluetooth is small speaker