Hi Rahul,
the best phone in your budget is the sony ericsson P1i
Its available at an amazing price of about 17,000 now.
its an amazing mullti tasker, good cam (3.2MP), u have the option of doing ur office stuff as well as play around with it (good music phone, cam etc)
You can get it with GPS at extra cost and buy a 16GB memory stick online.
That will fit your budget of 25k
check out www.p1iblog.com or read reviews online
Its the best phone ive owned so far, very stable, reliable and a mini PC on hands
SInce ur budget is higher, u can also get a sony G900. its got the same smartphone features of a P1i but is a little faster and has a 5mp cam