AT&T is ringing the changes big time for its iPhone and iPad subscribers. In a massive announcement, the company announced that it is calling it a day for unlimited data plans for iPhone and iPad users. Starting Monday, AT&T will abandon the unlimited plans and instead offer tiered data plans for customers. In order to cash in on the iPhone OS 4.0 media attention, AT&T has also announced that it will allow tethering on the new iPhone OS for an additional cost of $20/ month. Co-incidentally, Steve Jobs will showcase the new iPhone OS to the world the very same day (June 7th) when AT&T scraps its unlimited plans.

So, if you are an AT&T iPhone customer, how do these announcements affect you? First, you can no longer sign-up for the unlimited data plans from Monday. Next, you can choose from two new options – $15 per month for 200MB and $25 for 2GB (called “DataPlus” and “DataPro,” respectively). If you choose DataPlus, you pay $15 for each additional 200MB. If you choose DataPro, you pay $10 for each additional GB. If you are on the current $30 plan, you have the option to either continue it or switch to either DataPlus or DataPro.

AT&T’s theory is that nearly 98 percent of its subscribers will benefit from the new plans as they use less than 2 GB of data. This will entitle them to a saving of $5 to $15 on their current $30 monthly bills. However, if you are a heavy data downloader who enjoyed and exploited the ‘unlimited’ aspect, be prepared either to change your downloading habits or else prepare for deeper holes in your pockets, courtesy the new pricing plans.

To avail the tethering option from AT&T, you need to choose one of the new data plans. Further, it costs a whopping $20 a month. So, a DataPro plan with tethering now costs $45 per month. IMO, that’s a lot for 2GB of data shared between your phone and your tethered devices. All in all, it depends on how much data do you use? If you are a light user, you’ll gain from these changes. However, if you are an unlimited this-and-that addict, it’s definitely not good news for you. Further, tethering comes at a substantial cost.

Whoever said that all good things in life are free did not know about AT&T’s new plans for sure!