063 is not a country code. Numbers inside a country start like this: lifecell (Ukraine), AIS (Thailand), Telenor (Serbia), Abreulândia - TO (Brazil). 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 |
|---|---|---|
 lifecell · Ukraine | +380 63 … | 063 … |
 AIS · Thailand | +66 63 … | 063 … |
| DTAC · Thailand | +66 63 … | 063 … |
| True Move · Thailand | +66 63 … | 063 … |
 Telenor · Serbia | +381 63 … | 063 … |
 Abreulândia - TO · Brazil | +55 63 … | 063 … |
| Aguiarnópolis - TO · Brazil | +55 63 … | 063 … |
| Aliança do Tocantins - TO · Brazil | +55 63 … | 063 … |
| 72 more in Brazil | ||
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.