Actually, you can record someone without their consent (audio only) I do believe you have to notify them of the recording at some point, but you do not need consent for an audio recording. You only need their consent for video recording.
You have to tell someone they are being recorded whenever you start talking and there is a recording, you don't get to just state it at the end. Laws and common sense dictate this.
There are some “one party consent” states that allow you to record someone over the phone without their knowledge. I was surprised when I first heard this, but it’s true.
