Siri calls appear on speaker phone but not bt

[mccltd]

When Im in my car and the phones connected to the radio via bt if I initiate a call with siri it automatically goes to speaker phone.
I then have to manually select bluetooth.
Is there another command I should be saying to make it work via bt?

 

[cynics]

When Im in my car and the phones connected to the radio via bt if I initiate a call with siri it automatically goes to speaker phone.
I then have to manually select bluetooth.
Is there another command I should be saying to make it work via bt?

The best way I know is to say "Hey Siri call xxxxx using bluetooth".

I don't know when or why mine all of a started using the iPhone speaker vs bluetooth especially since I'm using Siri via bluetooth.