I had the same issue. The thing is, the 820 display the signal wrong with the wrong carrier.
When I was using Indosat in Indonesia, the signal is often on 3G or H but often fails to load a page.
Sent to Nokia service center, they could not fix it.
Now I am using Medion Mobile / ALDI Talk in Germany, the indicator is always correct. When its 3G or H+, the phone is always incredibly fast (both in data and battery drain)
So I think its more of an indicator problem.