We had a 3 hour window between connecting flights through Belgrade and contacted Dushan through viber explaining the exact time we have and what we wanted.
Dushan was pleasant, responsive, gave the exact price quotation we had to pay. Especially aapreciated was the opportunity to pay using card (we had no cash, and even if we did, sure not in Serbian currency). He had a card machine inside the car, so no problem at all.
We also had a last minute flight delay and were offered a discount on the initial price since the "tour" had to be shorter.
We were met at the arrivals exit with our name, escorted to a comfortable car with onboard wifi, and given a 1,5 hour tour through the night Belgrade.
We had an amazing time, would do it again definitely!
Thank you from Cyprus!