ah I see, there should be an adapter for the PC or for phone - if there is a single TRRS plug on the end, there should be an adapter to have separate audio and mic plugs like
this one or alternatively have 2 separate plugs on the headset and an adapter like
this one to use for phones.
It is possible you are not using the adapter to split the connectors to use it for PC, or are using the adapter for a single plug and using it on your audio output plug.
Which connections do the headset have?