Here is a big complaint about the AT&T international package and the usage of the web browser on hte iPhone while travelling:

IS THERE A WAY TO UNLOCK THE IPHONE TO SWITCH BACK TO ANOTHER PROVIDER?
In the past 2 months I have rapidly become a fan of AT&T hate club. I switched to AT&T from the dependable Verizon because of the iphone. Boy was that a mistake. It’s bad enough that my calls get dropped daily, average 3 times per day. I just came back from traveling abroad and found out that AT&T charged me $800 for internet usage that I never did and also all the calls that came in which I did not pick up. Apparently your internet browser needs to be absolutely turned off. If not, even if you are not surfing the internet, you are getting charged for all the data forwarded to your internet browser even when you did not use it at all. Also, if anyone calls you and you do not pick up the phone, you still get charged roaming. I had about $200 worth of calls charged at $1.29 per call simply because the phone rang and went into voicemail.
I did pay for the $20 international package so that I can read my emails while traveling. Big disappointment! My emails were so slow to download that I ended up not able to access the data because it took too long. Instead, I text. Which cost $.50 per text.
Lessons learned: AT&T = bad customer service, bad cell phone coverage, and misleading contracts.

Apparently more and more people are fedup by the quality problems that AT&T compard to the Verizon network.