0823 is not a country code. Numbers inside a country start like this: Sylhet (Bangladesh), Telkomsel (Indonesia), Kure, Hiroshima (Japan), Killa Saifullah (Pakistan). 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 |
|---|---|---|
 Sylhet · Bangladesh | +880 823 … | 0823 … |
 Telkomsel · Indonesia | +62 823 … | 0823 … |
 Kure, Hiroshima · Japan | +81 823 … | 0823 … |
 Killa Saifullah · Pakistan | +92 823 … | 0823 … |
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.