There may be some auto-gain settings we can adjust, but echo is usually caused by direct feedback in the headset itself. When the speaker is too loud or the mic level up too high, the callers voice is picked up by the mic and is too separate from the original sound to be removed via echo cancellation.
mic is the first thing to check, because turning down the volume on the
headset can make it just as unusable as echo. Often Microsoft will
apply a microphone +20db gain to mic inputs, and many headsets are
sensitive enough to not require that.