Firstly, there is no such verb as "хочеть". There is "хотеть".
Secondly, you may use it with both accusative and genitive cases but with a slight different meaning. "Хотеть" means "to want". So, if you want something as a whole thing or you want something in general you use it with accusative. For example: "Я хочу эту булочку". When you want a piece of something, usually a portion of some substance such as water, milk, tea, you use genitive case: "Хочу воды", "хочу чая". And this word is never used with dative.
But you have to know one thing. Some words as "чай" have two forms of genitive case. The usual form: "чая", and so-called partitive case "чаю". So you may often come across such phrases as "хотеть/выпить чаю" or "хотеть/выпить чая". They are both correct and both genitive.