For the use of taxi services from Belgrade Nikola Tesla Airport to any destination in Belgrade area and further, please contact the city service TAXI INFO desk, located in the baggage reclaim area. If this one is not working, there is one located immediately after you exit the baggage reclaim area, right next to the exit door.
Just be aware NOT taking the taxi from anyone who approaches you – they usually charge much more. Please take a taxi receipt at the information desk – it should state your end destination in Belgrade and the ride price. The price is fixed (1800 dinars for any location in the city center). See more info about the taxi here