When the iPhone was introduced in June 2007, AT&T's 2-year contract required a data plan—there was no cell-only option. But the pricing of $30 a month for unlimited data was groundbreaking. The carrier killed the unlimited option exactly three years later. Existing agreements are honored as long as you don't let them lapse, but all new users have to choose between a 200MB/month ($15/month) or 2GB/month data plan ($25/month). Going over your data limit is not cheap: $15 for an additional 200MB or $10 for 1GB, depending on your plan.