Celkon i4: GPRS Setting Problem

Hi,
i was looking to buy iPhone for me and when i come to know about the cost of Apple iPhone it's just out of my budget and then i decided to buy a cheaper one for me, i search a lot and atlast i got a new Celkon iPhone4 for me and it's quite good but the main problem i was encountering that i can't access net through GPRS and infact i couldn't able to Edit the GPRS settings. If someone nows how it works and has a best solution to my problem please let me know as soon as possible.