Same issue here. 2024 outback wilderness. Have tried restoring my phone and set up as new even the issue still persists. There are several other forums out there of hundreds of people having the same problem. It is not limited to iPhone Subaru acknowledges the problem, but does not provide a fix.
The only workaround is as someone above side, go to your call screen on your phone, switch to speaker or phone and then switch back to CarPlay.
I would encourage everyone here to please reach out to a Subaru. Customer advocate and share your complaints. They have offered to credit me $1000 service or parts credit.
Sucks because it still does not fix the issue.
Subaru customer advocate phone number is
800-782-2783
Please call and share your concerns.