You have a serious problem Blakw with your Xbox console you need to take help from Xbox one support team.

You can aso try the following steps also.

Remove the headset from the controller by unplugging the cable from the beneath of controller. Now connect the headset to the controller port directly.
Ensure that microphone is not silent. Take a look at the mute button from the left side of headset. This button is embedded on the front of your headset cable sometimes.
Go to device accessories from ‘setting’ menu and adjust the loudness of your headset plugged into 3.5mm jack.
If you find that your hardware is not working properly, then change the device with the new one.
Update your device software to experience better performance and speed. For update, you can take Xbox support from the official website.

If none of the above mentioned solutions work, then move on to Xbox tech support,