Actually this never happens with my BSNL BB. Happened once with my Tikona WiBro but they rectified the issue and it came up as the SBN to which I was connecting was recently brought from Delhi and deployed directly without modifying the settings.
I never observed this issue before with my BSNL 3g... I use to have a look at the speed test result which showed the distance to mumbai as ~50miles. so I am bit skeptical on this one....
And U know what..... When I get the Ahmedabad IP I cannot use mail.yahoo.com and yahoo messenger... whereas with the Pune IP I can use these services. Now this does bother me as I need Yahoo messenger badly during trading hours to discuss with my friends
Can only hope this resolves soon as it has worked out for others.