Switch to Speakerphone
When you’re on a call, you’ll notice the speaker button on the right side of your phone call menu. Tapping that switches back and forth between speakerphone. This is almost always worth a try when you are struggling with poor call quality. First, it adds a lot of volume and generally improves clarity, while also helping to counter some of the issues with obstructing cases and similar problems. Second, if the speakerphone doesn’t solve your problem, that’s a good indicator that the connection itself is bad.