iphone is stuck and is not switching off either

Hi. I was updating my iphone to the latest iOS version 9.3. Everything went smoothly, then it started verifying the update. A few seconds later, a message box appeared saying that iOS 9.3 failed to update because connectivity issues, and the verifying update sign was constantly showing on the screen. Because of that sign, I was unable to do anyhting on the phone, so I asked Siri to switch off the wifi because I thought that would help make the sign go away but after turning the wifi off, there was still nothing I could do. Even the iphone is not turning off. Now the phone is stuck and I am unable to do anything. Please help me with this and let me know what I should do as soon as possible. Thanks!