If you have any micromax 3G data card like MMX 352G, 353G, 310G or any data card with 3G capability means works on HSDPA network or HSUPA network, then you can use internet with 3G Speed in 2G data or GPRS plans. So you will have to do a simple thing:-
Open your micromax 3g software or USB manager
Now click on settings, you can see on screenshot
In the network mode, select HSPA/UMTS only setting
Now, you can try 3G speed with your 2G pack, but this works only in the area which is 3G enabled and you can try with all the networks like Vodafone, BSNL, Tata Docomo, Aircel, Airtel, Idea, Videocon, Virgin and any other company. I saw this trick in many of my friends who uses this trick with BSNL and Vodafone works very Fine.