How to cancel an update for Iphone?

What do i do? I pressed the software update for ios 6 on my iphone 4s. Then i forgot to back up my phone. How do i do that now? I can't go to my home screen because everytime i try to restart my iphone it keeps on saying that my phone should be plugged on itunes.

I'm sorry. Unfortunately there isn't a way to undo it. Did you do the update from the iPhone itself or on iTunes? If its showing connect to iTunes you need to connect it and restore. If it doesn't restore, turn it off and hold the home button down connecting it to the computer again. When iTunes recognizes the iPhone in recovery, try to restore again. If you updated thought iTunes it should have backed up before completing in which case you can restore from that backup