I have domains A.com, A.co.in and A.in Purchased from site X.

I have a hosting space/account purchased from site Y, which has provided me with 2 DNS entries that is to be replaced in the account at the site from where I purchase the domains.

I have successfully changed the DNS entries of A.com to these 2 DNS entries and I am able to see my index.html page when I hit A.com.

Problem

On similar lines, I have changed the DNS entries to the same entries for A.co.in and A.in, but on hitting those sites in browser gives me no response and browser specific page of 'Site not found' is been seen.

Please let me know, how to set this, so that when I hit any of the domain, the web-site is rendered from the hosting server? What am I doing wrong here?

Note

1. It has been more than 3 days after changing the DNS entries, so I don't think so this is a problem of DNS propagation, which I heard from some people.
2. Please provide some detail explanation, as I am very very new to this. This is my first hosting ;)

-Thanks