Here is simple trick to get Your 3G speed back.
Recharge your Airtel number with small video call pack (call customer
care for pack details) and enjoy 800kbps
speed.
if speed not get uncapped,then call customer care and tell them video
call picture quality is low.
soon they will be
uncapped your sim.
Now use any existing airtel gprs trick and enjoy 3g speed for free.
NB:If you dont have video call supported 3g phone then put your sim in
such phone and do as above.After testing,put the sim inyour normal 3g
phone.You will get the same 3g speed.