my hair is super thick too, and stylists also always tried to thin mine until i put my foot down (after too many disastrous cuts) and started telling them under no circumstances should they thin, texturize, etc.
a good cut can shape your hair without thinning it. long layers, and letting it get some length helps. i have found a modified cg routine to help the thickness aspect a lot too, as far as taming the bigness of my hair.
coarse, thick 3a