The manual for my Phonak L90 hearing aids cites a multi-function button, but all i can see is a rocker switch.
My agenda is to be able to answer a phone call without pulling my Samsung Note 8 phone (running Android 9) out of my pocket and unlocking it.
“Tap control” ought to be able to handle what you want. Phonak Support Community
The button might be able to work too. Talk to your hearing aid provider to see how they set them up.
On the Naida Lumity 90 BTE’s, one click down on the rocker switch answers any incoming phone calls…Cheers Kev 
confirm, the Phonak user manual does indeed indicate that the “rocker” switch you refer to is its “multi-function” switch:
You would typically press on the UPPER HALF of that rocker to change programs or increase the volume. Press the LOWER HALF of that rocker to lower the volume or f’instance, put the aids into MUTE (short press) or OFF (longer press).
To answer a phone call without pulling your Samsung phone out, just press the UPPER HALF of that rocker for a brief second. The call should come through.
To either DENY the call or hang up, press the LOWER HALF of that rocker for a brief second. As long as your Note is on, and you’ve paired + connected your aids to it through Bluetooth, you should be good to go!
I can assure you, I have a Samsung Galaxy Flip-4 Android phone, and can answer a call with the UPPER HALF press when I’m on a completely different floor of the house than my phone. The range - AND its Bluetooth reliability - is ROCK SOLID.
Answer is that it depends on the exact model and the configuration you got from your Audi.
The easiest is to ask for the printed report which the Audi can take out of the fitting software.
Out of the box, settings would be short press = volume up/down, longpress = program switch.
Double-Tap the default depends on the model.
