Once on a flight down under, I requested a climb from FL290 to Fl350...I had this clearance " maintain FL350 ". We asked for a recomfirmation that we were cleared to climb from FL290 to FL350, we had an agiatated " maintain FL 350 ". Skipper asked that we were currently at FL 290, are we to maintain that? Came another curt reply, " you are cleared to maintain FL350 ". Well, we reported " vacating FL290 for FL350 ", " roger " was what we got in reply. GO figure.................