Hello Killerz,
I have also asked for plan UL500, but they told me that it will be for three months period. Have you changed your plan to UL500 or Home 500? If it's Home 500, then the download limit will be calculated from 1st Dec. If it's UL500, then you will not have to bother. Actually UL750 has been reduced to UL500 for three months period.

And for Mandrin21, we get high speed in BSNL Broadband. How much speed you are getting in your connection?