Iphone X Using Phonak Hearing Aid App

Can anyone familiar with the Phonak Hearing Aid App and its relationship to the Iphone X address this question? I have this app connected to my iphone via bluetooth, and for the most part, it works as it is designed. However, when I go to SETTINGS>SOUNDS & HAPTICS> and click on the various alert and/or ringtones assigned (by me) to the listed functions, this is what happens. All of the text and alert tones play directly through my hearing aids clearly as the app is designed to do. But when I play the phone's ringtone, it comes out of the phone's speaker and will not play in my hearing aids. I have also tried this with many of my contacts, and the the same result occurs. Consequently, in order to answer an incoming call with my hearing aids (using the double tap method), I have to have the volume button on the phone turned off, so that the ringtone will reach my hearing aids. However, having the volume button disengaged has no effect on when I play the ringtones in the "SOUNDS & HAPTICS". They still only play out of the speaker on the phone. I wonder if there might be a setting on the phone that needs to be changed? My phone is updated to the latest ios. My audiologist has no idea why this is happening. Thank you, Jeff