Facebook Mobile Activation?

I keep trying to type "F" "On" and "Fb" (without quotes) to Facebook so I can activate mobile texts and get the confirmation code, but my texts aren't going through because I'm not receiving one. I've tried to contact their support but they offer no help. I've made sure all the things on their trouble shooting page are working but nothing is solving my problem. Anyone know why it's doing this? I used to have Facebook texts, but I deactivated it because it wasn't working right. Is it my phone or is it my profile?