I've got a 2010 infiniti g37x sedan, and I can't play music thru the usb cord.
I don't have the navigational package, so I don't have the option of streaming music through Bluetooth.

I plug my phone into the usb, it says "reading file" and then "there is no song" pops up.
My iphone software is up to date, I've called the dealer and they have no idea what the problem is.
Help please. Thank you

 

One of the primary functions of the built in USB port is a UI for iPods and iPhones.
Have you tried a different cable?
What iPhone are you using?
My kids have the 4S and 5 and they work. I use a Z30 and it also works (audio/video) via USB mass storage turned on, on the phone.