GMC Sierra Bluetooth volume

I’ve seen posts on this but not recently. I have a 2020 GMC Sierra and when my iPhone connects to the vehicles Bluetooth the ringer volume is turned down. And when I get out of the pickup, the volume is not restored. After reading a lot of suggested solutions, none of which had any effect for me, I believe that the issue is with either OnStar and/or GM. I can turn up the volume using the side buttons (cover off) and literally watch it immediately go back to silent. It’s very frustrating and it’s caused me to miss a lot of calls and texts. None of the Changes to phone settings helped. I’ve tried setting volume fixes and “change with buttons”. My solution I guess is to disconnect my phone from the vehicle (i Already tried a Disconnection/reconnection) and use my earpiece for hands free. Forget Apple play and the various phone features until this issue is fixed and I reconnect my phone to the vehicle. Total PIA