Good day Pat,
It sounds as if you may have an issue with the headset microphone connection to the iPhone. Since you say that the issue is present with multiple different headsets, that leads me to believe that the problem is with the iPhone itself.
I would suggest that you follow the steps in this article -
If your voice is too faint or sounds unclear using iPhone, or iPod touch - Apple Support
In particular the section titled Fix common issues -
Follow these steps, testing after each with Voice Memos.
- Unplug anything plugged into the headset jack.
- If you're on a call and holding your phone next to your ear, speak into the microphone and make sure you don't block it with your fingers or shoulder.
- If you're using a screen protector or case that covers the microphone, remove it. Clear any debris from the microphones.
- Restart your device.
- Update to the latest version of iOS.
If you've tried these steps and people still can't hear you well on calls, contact Apple Support.
Thanks for using Apple Support Communities.
Safe computing,
Brett L