I just purchased a cable that has a dock connector on one end and splits to a USB connector (for charging) and 3.5mm jack (for audio). I wanted the best quality audio in my car at a reasonable price. Plugged it in and immediately noticed better quality sound when playing music (than the headphone out). However, big problem, when using the phone I get no audio out through my car speakers - the sound just comes out through the phone. Any ideas on how I might fix this please?