LG VX-8600 / AX-8600

I went and bought the cheap adapter so I can listen to music from my 8600 through my Truck radio- and boy does it sound great 🤤 . However, I got the bright idea that it's cool that I can listen to a call through my truck speakers. However, since I'm using an adapter that plugs into the 3.5mm spot on the adapter that plugs into my 8600, it treats it as a headset, and therefore doesn't hear me (I tested by calling my voicemail and tried to record a new personal greeting).

I didn't try speakerphone yet 👀 . Just dawned on me that it might work that way. If not, is there a way to use my phone in a handsfree format through my Aux-In on the truck stereo unit? Thanks ahead of time.