I drive a 2002 honda civic and i have a alpine stero with a usb connector?

I can listen to my music on my ipod but i can't listen to my music on my phone
says a device is not connected but my phone is charged (obviously)

Which Alpine head unit does the car has? Which phone you have? Most car stereo USB ports can only read mass storage devices. Your phone perhaps doesn't use mass storage mode over USB, so unless your stereo speaks MTP over USB, I don't think you'll be able connect to your stereo. Bluetooth? Synchronizing problem?

The Display Audio Interface on most newer units is used for direct connection to and streaming from some current smartphones. Some smartphones may not work. Please see your Alpine dealer for details. Or:
http://www.alpine-usa.com/product/category/av-head-units-head-units

Edit: Hope I have given to you some small ideas. The question is not really include the needed to know information so I've tried to answer.