Sorry to hear that it didn't help. Regardless it seems like eating, coffee, exercise makes phlegm production worse and it lasts a couple hours. Need to avoid these activities prior to speaking to people at work which is frustrating.

Has anyone tried oral prednisone for a couple weeks combined with fluticasone spray?
Saw this article on pubmed where 4 day course of Prednisone 30mg allowed immune system to revert somewhat back to a more balanced state.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8614904/#:~:text=A%20short%20course%20of%20corticosteroids,be%20effective%20in%20this%20situation.
I'm not sure if this will apply and regulate what is happening with the ENT region and long covid immune over-activity (that we assume).