Using this trick you can get 3G speed on 2G plans.
Just follow these steps :
First Activate a 2G Gprs plan on your 3G Docomo Sim
Then make your balance to a level RS 1-2
Then type *141# and choose the cheapest plan .
Then they will inform you that you have no sufficient balance to activate the plan .
Just ignore it. open your browser and check the speed
Now , 3G speed on 2G plan .
That's it .