0999 is not a country code. Numbers inside a country start like this: Yining, Xinjiang (China), Aptel (Iran), Movistar (Peru), Smart (Philippines) 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 |
|---|---|---|
 Yining, Xinjiang · China | +86 999 … | 0999 … |
 Aptel · Iran | +98 999 … | 0999 … |
| IR-MCI · Iran | +98 999 … | 0999 … |
| Irancell · Iran | +98 999 … | 0999 … |
| 1 more in Iran | ||
 Movistar · Peru | +51 999 … | 0999 … |
 Smart · Philippines | +63 999 … | 0999 … |
 Indochina Telecom · Vietnam | +84 999 … | 0999 … |
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.