ETravelSim does not offer a truly unlimited data eSIM for Serbia. Plans that carry the "Unlimited" name provide a fixed allowance of 4GB/day; after this daily limit is reached, high‑speed data is reduced to 128kbps according to the plan details.
The provider does offer fixed data plans that give larger fixed allowances. For example, the Travel eSIM for Europe 50 GB – 30 days / Data Only gives 50 GB for 30 days at a price of $29.19 USD and does not throttle speed after the data cap. Another option is the Serbia eSIM Unlimited – 30 days plan, which offers 4GB/day for 30 days and applies the reduced speed after the daily limit. Choosing a fixed data plan can provide higher speed and may be more cost‑effective for heavy data users.