iPhone SE call volume

Since late in the iOS 11 release cycle, the volume during a telephone call on my iPhone SE has been too low. Has anyone else noticed this issue? I am a beta tester, and have reported the issue to Apple using Feedback during iOS 12 beta.

Specific details of the issue:

• While in a call, I can turn the volume up or down, but it never goes louder than some preset maximum. This preset maximum is too low in many situations, for example, if I'm in a noisy public place or talking to someone with a soft voice., it's impossible for me to hear the person on the other end of the call.
• The problem only occurs when I hold the iPhone to my head. It is not an issue on speakerphone or with earbuds So, the workaround is to use speakerphone or earbuds so that I have adequate control over the volume.
• The problem also occurs when I retrieve a voice mail.
• The problem is not related to accessibility, and occurs regardless of whether VoiceOver is on or off.
• The problem occurs regardless of whether I've placed or received a call.
• There are no other audio problems with this device. Music plays normally under all circumstances, VoiceOver volume works as expected, etc.

Anyone else with similar volume issues, please share. Or, I'm also open to any tips that might resolve the issue.