I thus have to resort to using Citrofresh products to fight against them. And it works miracle; not only keeping the White flies abate but also boosts plant growth so much! Sadly, you couldn't get this Plant Synergist in Singapore easily. I got the product only because brother had previously helped in the marketing of it.
As an alternative, i was advised to constantly spray water at the leaves to keep the flies away and to flush away its eggs on the underside of the leaves.
It's a short-term measure but at least, it keeps my plants alive.