To be honest, I can't understand either the English or the Japanese.
'throw trash' ? Were they throwing trash -at- you? Is this shorthand for 'throw out trash'? Is it a way to say 'litter'?
I think you also may be misspelling なげる as なける, if your meaning is indeed that they were throwing trash at you or out the window.
I don't think のに or まま make sense here, のに because it has the wrong tone. のに is like 'even though', the part after のに being contrary to expectations implied by the part before のに.
まま is simply not used in this way at all. In any interpretation of the English, it's not a continuous state, it's an intermittent action. (If you rephrased it to say 'upstairs neighbor continues to be a litterbug' then the Japanese of that might use まま, but I don't feel able to write that sentence in Japanese with any confidence.)