De or het supportafdeling?

The correct Dutch article is:

de supportafdeling

Rule Words ending in -ing: almost always de. See the rule

How to use supportafdeling

the supportafdelingde supportafdeling
this supportafdelingdeze supportafdeling
that supportafdelingdie supportafdeling
our supportafdelingonze supportafdeling
your supportafdelingjouw supportafdeling
every supportafdelingelke supportafdeling
which supportafdeling?welke supportafdeling?
a big supportafdeling / the big supportafdelingeen grote supportafdeling, de grote supportafdeling