Same issue here. Initially I got speeds of about 4mbps but now they have dropped to 0.7mbps which is even less than what I get at 2G. I called them up and they later sent a message that there was a temporary connectivity issue which has now been resolved. Alas, the speed didn't increase. Later, I complained again and gave details of the exact location and phone after which I received a call saying that my 3G Services were not activated earlier and have now been activated. So they automatically deactivated my 3G services even when I was on a 250 rs 3G plan? Now their message says 3G will be active in 4 hours so I am hoping that I will get back the speeds again.
I think you can message 3G to 121 to check if your 3G hasn't been automatically deactivated by them.
Just to update my 3G wasn't automatically deactivated by them - they gave that just as a LAME excuse and I continue to get 0.07 mbps compared 3.5 mbps + that I used to get 15 days back. After many days of calling, I've given up - going to deactivate the plan before the renewal date comes up. It feels like my speeds are limited to 0.07 by policy. It's like a FUP: if you cross 500 MB in your 1GB data plan, we will reduce your speed !