Delete it or get it to stop? You can't uninstall or delete it, and it's not on unless you tap the button during a call. Are you sure you don't mean live transcribe? Can't uninstall that either, but it's not active until you actually activate it.
Go into the phone settings (or accessibility settings), find real time text, tap it and where it says RTT button, tap that, make it visible at all times, then tap the button to turn it off. The default is to be visible during calls, and you may have hit it by accident on a previous call. If you choose not to change the visibility setting, you can wait til you make or receive a call, tap the button and turn it off.
