Airbus 350 in X-Plane 11.50. Flight from Kuala Lumpur (Malaysia; WMKK) to Nadi (Fidji; NFFN). Initial altitude FL350. About half way, ask for FL370. Controller replies "Unable", this altitude is TOO LOW for my route and instead clears me to FL590! I check the speech to text and my request was correct. I request FL390, hoping that this request would trigger something, to no avail. I say "Unable FL590", and still no joy. For the last half-hour, the controller has been repeating "[Call Sign] climb and maintain FL590" and then "Expedite climb to FL590". I know for a fact that NO airliner is able to fly at FL590; even a Concorde, most of the time, could not make it to that altitude. Beside the obvious bug, is there anyway to tell the controller to quit the broken record?