I canceled my AT&T account a few weeks ago. I have a four line Sprint contract that has another year before I can cancel. I was tired of paying the extra $66/month. So my iPhone now has no service. I plan to continue using it as an iPod Touch until my Sprint contract can be canceled and then I'll go back to AT&T. My question is - will I be able to upgrade my firmware? If I try to upgrade won't iTunes see that I don't have an account and require me to activate before I can use the iPhone?