Are the insects very tiny (almost like very small grains of soil) and live on the under side of the leaf?
Those are tought mfs and you first need to isolate the plant.
I have a 50% winning record against them. I wash every leaf and the bark with a ‘green soap’ and water combination and paper towels. Once I even submerged the plant upside down in the same combination.
Fair. But you are asking us to trust your word when you could provide us with some links.