iPhone 8 Plus static

I’m getting a constant static noise when making and receiving calls. Tested with my wife’s phone. Sometimes you can’t even hear the speaker. While Playing music there is no static. The phone lives in a otter box defender. Never gets wet. Tried updating it to the most recent update and the static is still there. Problem started about 3 days ago. I live in Louisiana and it’s been above 90 degrees. Don’t know if that’s the cause.