Hello and welcome to Apple Support Communities Gls1066,
Thank you for contacting us. You have come to the right place and we are happy to assist you. We understand you're having an issue with sound quality for outbound calls. We can understand why you’d reach out for a solution. To start, make sure you have the most current Operating System on your device. (Settings > General > Software Update) There are some great steps to try here especially "on Face Time calls": If the microphones on your iPhone aren't working
Many audio issues are carrier related, but if they are intermittent or only in specific areas, it can also be a network issue. After going through the steps above and contacting your carrier, and still having issues, please reach out for further assistance.
Thank you for contacting Apple Support Communities.
Best regards.