091 is not a country code. Numbers inside a country start like this: TriMob (Ukraine), Team Telecom Armenia (Armenia), AIS (Thailand), Bellinzona (Switzerland) 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 |
|---|---|---|
 TriMob · Ukraine | +380 91 … | 091 … |
 Team Telecom Armenia · Armenia | +374 91 … | 091 … |
 AIS · Thailand | +66 91 … | 091 … |
| DTAC · Thailand | +66 91 … | 091 … |
| TOT Mobile · Thailand | +66 91 … | 091 … |
| 1 more in Thailand | ||
 Bellinzona · Switzerland | +41 91 … | 091 … |
 Abaetetuba - PA · Brazil | +55 91 … | 091 … |
| Acará - PA · Brazil | +55 91 … | 091 … |
| Americano - PA · Brazil | +55 91 … | 091 … |
| 70 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.