what vehicle is it installed in? If It's a Chrysler that is factory amplified and you are retaining the factory amp by using a metra adapter, then what may be happening is all the audio is actually coming from the rear outputs of the radio. The front outputs are not really used by the metra adapter. The telephone audio over Bluetooth is only sent out over the front outputs of the Pioneer. So since the cars amp never sees the front outputs you don't hear the phone call. The simple fix is to reverse your speaker connections. Hook front to rear and rear to front. Then you'll hear the phone call.
