Hey there JenT426,
Thanks for reaching out to Apple Support Communities. I understand you’re having some issues with the audio from one of your iPhone speakers. I’ll be happy to help with this.
To verify, after factory restoring your iPhone, did you restore a backup to your device, or did you test the issue out in factory settings?
If you restored a backup, restore it to factory settings:
How to back up your iPhone, iPad, and iPod touch
Restore your iPhone, iPad, or iPod to factory settings
Then go through the steps in the following link, and test again:
If you can't hear a person on a call or voicemail or if the sound isn't clear on your iPhone
Let me know if this helps.