I have a 2006 Chevy Malibu and I want to play my music through Amazon Prime Music or Spotify, using my iPhone 7?

(which doesn't have an aux jack anymore). The car doesn't have an auxiliary port, a cassette deck, or Bluetooth capability. I know there are FM transmitters, but I've heard they're unreliable. Are there any products out there that would allow me to use Bluetooth or aux without buying a whole new stereo?

No. You will have to purchase an aftermarket audio deck with Bluetooth technology.

Is there an aux button on the head unit? Then there's a port in the back that will take an adapter. You just have to find the right one.

You can use a hardwired FM modulator. It's similar to an FM transmitter but much more reliable, because it's connected directly to the antenna jack at the back of the factory radio. When your music is playing, it cuts off the outside antenna signal and feeds your music in instead.

Search online for an IS7705. That's a model that will work with your iPhone. Some models include Bluetooth; those would work too.

Apple scrood you again. Unless you install an fm modulator for an aux input, then plug a bluetooth receiver into that to pick up the phone via bluetooth, the problem is apple world vs 3rd dimension world.