Need to use external microphone on FaceTime with iPhone

I have an external mic that I want to use for conducting 1-on-1 language learning sessions over FaceTime. I have an iPhone 14 Pro and DJI Mic 2 system. Mic receiver has a lightning connector, and I can connect it just fine to the iPhone. However, I can’t find a way to use the external mic as the audio input and my AirPods only as the audio output. If this can’t be done in FaceTime, is there another app that will allow me to split the audio input/output?