Hi Nowah101,
If you want to keep the volume up for your calls but don't want your iPhone to make a sound when receiving a notification, it is the case you will need to turn off sound for each app. Change notification settings on iPhone.
As a work around, you can use Focus to silence notifications and let calls come through Allow or silence notifications for a Focus on iPhone.
If you don't want the notification for a phone call either, you can set the iPhone on silence or set up the action button to silence the phone:
Ultimately, if you want to provide Apple with feedback on this feature, you can do so here Product Feedback - Apple.
Take care.