To use this trick you have to buy new reliance 2G SIM but it is rare.Check the SIM whether the Reliance RIM GSM Prepaid SIM is activated or not.
When the SIM get activated recharge with Rs99 mobile Net pack.If the recharge is successfully done you will get 2.5GB data usage valid for 30 days but you can use this pack only in mobile with 2G.
The trick is here now call the reliance customer care and convert your 2G SIM to 3G.
They may say your request will be processed shortly within few hours.You will get 3G speed when your 2G SIM is converted to 3G.But you should turn the Network Mode into UMTS or HSPA.
After 30 days if you again recharge with 99rs pack then you mayn’t get 3G speed but get 2G speed.So if you want the 3g speed again then buy a new 2G Sim and try it again.