Got Root aphids fungus gnats and springtails

So I checked my dirt today 7 days after transplanting to new containers with new dirt and found they were already infested with fungus gnat larvae a few root aphids and some springtails. I have tried everything I can think of to get the bugs out of my dirt but have not been successful.
I have drenched with gnatrol, mosquito dunks, and organicide. Applied de and used mulch. At best they just get slowed down. Actually everything ceased activity for a week or so then they just come right back. Im looking for something I can do to prevent the infestations. Im probably going to switch out the topsoil again in a day or so. But who knows how I’ll keep them from getting in my dirt again. Does Anyone have an idea for a preventative measure?

Springtails aren't a problem, I think . For fungus gnats I advice using s-f-nematodes (steinernema feltiae). They also work against thrips to some extent.

Gnatrol and Nematodes are your friend. Trust me.

Spinosadin a-d highest percentage you can afford and submerge pots in 5 gallon bucket 2 times a week..

Spray toiwt bowl holes and washing machine drains and sink overflows.

Maybe you're overwatering.
Be sure to let your soil dry out between waterings.

Imo mulch layers indoors have the tendency to keep your topsoil layer to wet.
It's in that area that the gnats thrive. It's for this reason I don't like to use mulch layers for indoor grows.

Also hang some yellow sticky papers for the flying gants.