I hear myself on an iPhone voice call

Please contact your Carrier. This is not an iPhone settings issue as you said this is happening on Voice Calls.

• Sometimes, weak signal or network congestion can cause audio to be routed back to you, creating an echo effect.
• Carrier settings updates can sometimes improve call quality. To check for carrier updates, go to Settings > General > About. If an update is available, you'll be prompted to install it.
• Ensure there are no physical obstructions around the microphone or speaker areas of your iPhone, such as a case or debris.
• During a call, try toggling between the speakerphone and regular phone mode. Additionally, check if the issue persists when using headphones or a Bluetooth headset.