iPhone won't route calls through lightning aux cord

I've recently purchased a new lightning-to-aux cable adapter to use with the aux cable in my car, which has less-than-par Bluetooth audio. When I plugged it in for the first time, a prompt on my iPhone asked me if the lightning adapter I had just attached was "Headphones" or "Other." I tapped Other, and now my phone won't play calls over my car speakers or use my car's microphone, anymore. Yesterday I used a different lightning-to-aux adapter with the same phone and same car and it worked fine, so I am 99% certain that by choosing "Other" I told my phone that my car's aux did not have a microphone. How do I go back and change this setting without buying a new adapter?