how to fix No service error

Did you actually buy a factory unlocked and contract free iPhone from the U.S.?

The way you put it, it implies that someone has actually done "factory unlocking" on your iPhone, which is not possible. Factory unlocked iPhone is sold on Apple online stores in the U.S.

** One should not receive "No service error" on factory unlocked iPhone, unless the SIM is faulty; unsupported carrier or it's a locked phone to a specific carrier.

Which carrier in India? Is it a carrier that actually supports the iPhone?

Vodafone is not a supported carrier in India. Aircel and Airtel are.

Anyway, it should get activated on Vodafone network. Try activating it using another network's SIM card, if it does, replace your Vodafone SIM card with a new one (could be a faulty SIM).

See this post. The user experienced the same issue. In the end it turned out to be a faulty SIM from Vodafone India.

https://discussions.apple.com/thread/3920987?answerId=18283078022#18283078022

i have a iphone 4 network not available carrier not available .and i live in st.vincent thats in the caribbean what should i do to get my sim work