One of the first things I did after upgrading to iOS 5 was cancel my unlimited text message plan. I used AT&T's "manage features" option on their website to do this. However, over the weekend, I noticed I was not getting any responses from the text messages I was sending to people. I figured out that I was not able to send or receive standard text messages. But I was able to send and receive iMessages. Apparently, people are having an issue with iOS 5 because they have too many text messages and going over a now-imposed limit. However, when I upgraded, I restored as a new phone. I didn't have any text messages to start with! So I don't think that's my issue. After restoring again to no avail, I figured out the solution. I went back on AT&T's website and re-enabled the $20 unlimited text message plan. Miraculously I was able to now send and receive text messages! What is the deal with this? Is AT&T disabling text messages if you don't have a text message plan but are using iMessages instead?