I experienced a new tactic. I had to phone Premium Bonds. Got all the usual stuff about delays etc., Waited for half-an-hour (driven mad by terrible music interrupted by monotonous recordings) then, finally, got through to a human. I started to explain my problem when I was interrupted by the human saying 'I can't hear you'. I repeated what I had said in a louder voice only to be interrupted again by the human saying 'I can't hear you, I will have to hang up unless you respond'. Click.
Probably tea break time.
I had made several phone calls that morning so I knew there was nothing wrong with my phone.