On my iPhone 3GS, iMessage recently started sending it via email. I've tried everything and I've checked Send & Receive and it won't even let me click on my phone number as an option. It also says "waiting for activation", under the option of turning iMessage on. How do I fix it to where it says my phone number and not my email?
I've found the best solution to these iMessage and Face Time woes is to just turn the service off, then back on again. That causes it to re-activate with Apple's servers, which should register your phone number as a usable iMessage sender.
The "Waiting for Activation" message suggests that this process wasn't completed properly, and/or there's some issue with Apple's servers. Try toggling it, and if it still doesn't work, try it again later, as it may be a server side issue that you need to wait for Apple to resolve.
I fixed the issue I had following this method using iTunes: