WP_Query to display only category names (without child post)

Hi there,

I am having a problem and after 2 days wasted searching for a solution it is my last bullet. My project has a listing page which should bring all the customer names. Those names have this structure:

Category Clients (ID=90)
Subcategory Lufthansa
Subcategory BMW

What I need is from the WP_Query or the template handling print only the name of the subcategories of clientes, but not the posts which are in these categories.

Note: I need to do it in this way because I am using a function to bring the content by ajax, to make the effect “load more”.

I would appreciate so much any answer, even if is to say that is not possible.

Thanks people