I am planning to get iPhone 4S but not sure which data plan is better for me in terms of cost and data use.  AT&T webpage shows the difference of $20.00 between 2 GB and 4GB data plan which I think is big difference for students like me. Can anyone suggest me which data plan should I buy? I will have wifi available most of the time and If I need to download data for somewhere else that will be basically for email checking.