iPhone USB Radio goes from playing Spotify to itunes

[Theonlydogtag]

So when I installed my radio in my car (Sony) I got the USB cable in a went to Spotify to play music. But came up with "no music". After weeks of pain I thought let's see if it works with ITunes. And it worked! Then it let Spotify work through USB too. This was great until everytime I connect my phone I now have to open iTunes play a song then go Spotify then I can play music. My main problem now is if I use the radio controls to skip a song it goes back to the iTunes playlist when I was listening to Spotify. And way of fixing this or shining so light on my over complicated way of listening to Spotify would be great thanks.