No, legally, it belongs to the apartment complex. Technically, anyone adding/removing to the dish would need to contact the apartment complex; this includes the tech who installed the other customer to this dish and if the existing customer wants to disconnect it. The tenant has ZERO rights outside his occupied space (for the argument that its "on my property" only works if its on his balcony/porch). There are good reasons why when you move, Dish/Direc tells you to leave the dish behind... and one of those reasons is because once something becomes affixed (IE: the dish, whether its pole or on a mast), it legally becomes a part of the property.
First, you need to talk to the apartment complex to make sure they did not authorize the tenant/tech to use THEIR dish, then take it up with DirecTV.
Yet another reason why techs, HSPs, tenants and management lothe apartment installs