Go For Wi-tribe..
they r also offering usb device
pakages
512kb -7GB -rs750
512kb -10GB -rs900
512kb -14GB -1200
1mb -14GB -rs1350
1mb - 17GB -1600
Zero Activation charges till 31 dec..u have to give one monthly advance payment..which is refundable.
service is gud.em using it from 31 oct 09
...i have used wateen 512..n now em using witribe 512..n i can easily say witribe is better than wateen
n the thing which i like the most is lowest extra volume price Rs.75/500mb..n xtra volume is valid for 30 days from activation