0154 is not a country code. Numbers inside a country start like this: Sriganganagar, Rajasthan (India), Kushiro, Hokkaido (Japan). 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 |
|---|---|---|
 Sriganganagar, Rajasthan · India | +91 154 … | 0154 … |
 Kushiro, Hokkaido · Japan | +81 154 … | 0154 … |
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.