0931 is not a country code. Numbers inside a country start like this: Würzburg (Germany), Lanzhou, Gansu (China), Nalitabari/Nakla/Sherpur (Bangladesh), MTCE (Iran) and others. The first digit 0 is the trunk prefix for domestic calls and is dropped from abroad.
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| Area or operator | From abroad | Inside the country |
|---|---|---|
 Würzburg · Germany | +49 931 … | 0931 … |
 Lanzhou, Gansu · China | +86 931 … | 0931 … |
 Nalitabari/Nakla/Sherpur · Bangladesh | +880 931 … | 0931 … |
 MTCE · Iran | +98 931 … | 0931 … |
 Claro · Peru | +51 931 … | 0931 … |
 FarEasTone · Taiwan | +886 931 … | 0931 … |
| Taiwan Mobile · Taiwan | +886 931 … | 0931 … |
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.