The ETravelSim Serbia eSIM works at Petrovaradin Fortress, the EXIT Festival main grounds, and across central Novi Sad with reliable 4G coverage. During EXIT in July, network congestion at the festival peaks may cause slower speeds for everyone regardless of carrier — this affects all networks because of the dense crowd of 200,000+ attendees in one location. For festival-heavy trips, the 25 GB or unlimited plan is the safer pick because of higher peak-time consumption.