idea 3g - GPRS 3G

the main problem i am facing with idea card is with the GPRS(3G) service, always it shows more usage then what i am using actually, always i use to contact on 4999, but i am not satisfied with their answers, as if once i used 2.38 GB and to the customer side it shows around 3.5 GB. I have a application which shows me how much data i have used. I went to idea office also, their in 599 Rs. they r giving 2GB usage normally, and the customer executive tells me that your plan is of 599 Rs. with 1.2 GB only( why is it so), different answers i always get from different places. The executive tells me that you'll get 1.2+1.2=2.4 GB usage plan, but according to office where i went they offers me normally 2GB usage, so if i activate from there then i should get 4GB of usage. M fed up with this confusion also that how much data i should use. my mobile number is 9763504898.
please send me a proper detail(as vodafone gives with all the calls and GPRS usage) bill on my email id nalodaria21@gmail.com
please give your valuable attention to my issue.