812 is not a country code. Numbers inside a country start like this: Ahal (Turkmenistan). The first digit 8 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 |
|---|---|---|
 Ahal · Turkmenistan | +993 12 … | 812 … |
| Area or operator | From abroad | Inside the country |
|---|---|---|
 St Petersburg · Russia | +7 812 … | 8812 … |
 Aurora, IN · United States | +1 812 … | 1812 … |
| Austin, IN · United States | +1 812 … | 1812 … |
| Batesville, IN · United States | +1 812 … | 1812 … |
| 71 more in United States | ||
 Panzhihua, Sichuan · China | +86 812 … | 0812 … |
 Ersekë, Kolonjë · Albania | +355 812 … | 0812 … |
 Telkomsel · Indonesia | +62 812 … | 0812 … |
 Airtel · Nigeria | +234 812 … | 0812 … |
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.