Raptors/F-150's had this same issue. On the Raptor Forum, someone posted that the adjustment needed to be made via phone settings. I cannot remember the process, but when I followed the directions (iPhone 6S here), it resolved the issue. And because my phone was adjusted from my Raptor, I have not had an issue in my Ram. Some of you may want to search that forum, or on-line the resolve it, as I do not believe its a UCONNECT issue.
I just did a quick google search, and this cut & paste is exactly what I adjusted for the Raptor...specifically the Change with Buttons bit
CarPlay ringer volume is painfully loud. … - Apple Community
https://discussions.apple.com › thread
Jul 22, 2017 - 37 answers - 8 authors
I figured a way that solves the loud ringing issue. Went to Settings- Sound- to section that says “Ringer and alerts”. I turned that way down. * You also have to switch the “Change with Buttons” to OFF.