This sounds more like a iPhone problem not the Volt or CarPlay. Most problems with audio and iPhones can be solved by performing a reset of the phone. Hold Down the power and home button until you see the screen blank and wait for the apple logo pop up then release.
My guess is this will fix the problem. Also make sure you are using an Apple certified USB to Lighting cable.
My guess is this will fix the problem. Also make sure you are using an Apple certified USB to Lighting cable.