Ziggs

Looking for some help! I just bought a 2019 GTC recently and have been having issues with my iPhone when plugged into the USB. Originally the car could not read the iPhone's music. I read on another thread that you need to have one song downloaded in Apple Music for the system to recognize your phone. I did this and it worked, it allowed me to use Amazon music. The issue I am having now is when I switch songs on Amazon Music it goes back to Apple Music to play the one song I downloaded. Does anyone know a work around for this and why the Mercedes System needs an Apple Music song downloaded as well?