It may be helpful to tell us what you've tried first, then someone could perhaps offer some advice.

Snails live in moist environments. Are you watering your garden quite a lot?
Mulching helps. They do not like to glide across mulch.
Diatomaceous Earth is all natural and will kill them. It just needs to be applied while the ground is quite dry and re-applied after rains.

GGG

Perhaps set up a toad friendly environment. Toads love to eat snails. Toad like a place to hide/burrow.

Here is a link that might be useful: {{gwi:827693}}