yes, you can add the data plan ($34.99) to a pre paid account on Tmobile. I have been doing that on my iphone since last December. I also just had my data "forcibly" upgraded from the $20 unlimited data/text to the $34.99 data plan. Brings my total to $86 per month. I'm okay with the bump, its still significantly cheaper than AT&T's options. I was just upset at their draconian style of the upgrade. One morning, my data stopped working and when I called to get help, they told me I needed to talk to Tech Support to upgrade to the appropriate plan. This was mid billing cycle and I had to go through several levels of customer service to get anything remotely acceptable. Usually Tmo is great, but the rollout of this change was so poorly excuted. I would have been fine with it, had I received notice in advance. 1 strike for Tmo, but for almost a year on them, thats pretty good having been with AT&T, Sprint and Verizon.