Is it possible to send and receive sounds to iPhone to mixer?

I am a radio broadcaster. The thing is I broadcast from home using Barix Annuncicom 100 as intercom connecting me to the radio station via internet. I achieve great result as if I'm sitting the studio at the station.

The problem is I have a co-host who called in to my phone, which I plug in the input slot on my Xenyx q502usb. I also achieve very good result, we -- my co-host calling in plug in from iPhone and myself both sound mixed by

Xenyx q502usb sending via Annuncicom 100 to the radio station.

The problem is because I plug in iPhone into one of the input slots, the sound from the mixer doesn't get sent back to the phone. My voice, while chatting with the co-host get through to the phone from the iPhone microphone and not from the microphone I plug into the mixer.

On top of that, my co-host cannot hear any sounds from the radio station; i.e. the jingles and so on. Someone suggested me get lighting jack to USB camera for iPhone, which I did and I plug this into Xenyx q502usb via USB port, it also doesn't work. The sounds travel one way, either in from the iPhone or out to the iPhone.

What should I do to also get sounds to and from iPhone, via either USB or any other channel from Xenyx q502usb?

Your advice would be greatly appreciated.