I wish I knew, Amazon are sticking with the line that I enabled it and I'm sticking with the line that I didn't because that's the truth. They say they've disabled it from their end but that I had to do some things at my end. I began to follow the instructions but a dialogue box came up immediately saying my Call facility had been cancelled and would I like to reconnect. The only options were Yes or Cancel, and Cancel made the dialogue box disappear but got me no further with the protocol I was supposed to follow. I logged out as required, logged back in again also as required, but I've no idea if it's gone. I'm thinking maybe not as there's nothing in settings to enable it. I've told Amazon but I'm glad to have your comment as this clearly isn't just me and neither of us activated it.
Also, like you I'd said nothing to trigger it. The radio was on a music station which does have some speech, but given it had to both use the wake word AND trigger the call using my name, I'm not convinced this was feasible.