0257 is not a country code. Numbers inside a country start like this: Aragats, Aragatsotn (Armenia), Jalgaon, Maharashtra (India), Kashiwazaki, Niigata (Japan), Arad (Romania) and others. The first digit 0 is the trunk prefix for domestic calls and is dropped from abroad.
Have the full number? Check it in the number lookup.
| Area or operator | From abroad | Inside the country |
|---|---|---|
 Aragats, Aragatsotn · Armenia | +374 257 … | 0257 … |
| Tsakhkahovit, Aragatsotn · Armenia | +374 257 … | 0257 … |
 Jalgaon, Maharashtra · India | +91 257 … | 0257 … |
 Kashiwazaki, Niigata · Japan | +81 257 … | 0257 … |
 Arad · Romania | +40 257 … | 0257 … |
 Portuguesa · Venezuela | +58 257 … | 0257 … |
 Phu Yen Province · Vietnam | +84 257 … | 0257 … |
If a number starts with +, the first 1–3 digits are the country code. If it starts with 0 (8 in Russia and Kazakhstan), it is a domestic number: an area or operator code follows, and from abroad the 0 or 8 is replaced with + and the country code. The same digits can mean different places, so where the call came from matters.