I was about to activate 375Rs 500MB 3G data plan. But I learnt from CC that plan data usage is counted against 500MB only when using 3g network. When using 2G network the data usage is charged at 10p/kb. This is ridiculous. Vodafone doesn't have 3G in all places and indoors the 3G signal is mostly very weak and automatically switches to 2G. With this network status its unfair for Vodafone to charge seperately for 2G data usage.
What everyone else is doing who have activated 3G Plans? Are all providers doing the same?
btw I am from Bangalore.
I think the CSR has been confused by the use of 2G and 3G and so on (don't worry, I face the same problems whenever I even open my mouth at a CSR or even tweet about them).
Anyway, to answer your question, when your phone can only achieve EDGE (2G) speeds due to their 3G coverage not being available in that location, your data will still be counted as per the plan, so long as you're not roaming. The only difference is that instead of being relatively nice and snappy, it goes painfully slow.
The thing is that your SIM is activated EITHER for 3G OR 2G, not both, and then the only variable is whether your nearest tower is sufficiently close to where you are at any given moment as to whether or not your phone will get a 3G signal or drop back to a 2G signal because of distance or stuff being in the way, like buildings.
Source: In my in-laws apartment, Vodafone 3G reaches only about 30cm inside the balcony, drops back to 2G for about 2m and then the signal dies completely - but I've never been charged a different rate for using my 3G plan while only achieving a 2G signal.