It is not a good idea to repot that type of cacti below the level it was originally planted. That rarely works well and usually leads to the plant rotting after it is watered. At least that has been my experience. It's also best not to water for the first two weeks after planting to allow any roots damaged during the potting process to regenerate.
I am curious as to the reason you might want to plant it deeper in the soil than it already is?