When I plug my iPhone into car intunes starts to play instead of spotify, how do i fix?

[mike212916]

Iphone 7 on iOS 11.0.3 trying to connect to my car via USB cable. 

Before when I plugged in my phone spotify would start playing. 

Now when I plug in my phone my itunes music starts to play. 

"even when spotify is opened and playing a song before i plug it in" it still goes and opens my itunes music. 

how do i switch it back so it goes automatically to Spotify?