Why do call center staff always pretend they can't hear you?

My V6 box has stopped working since yesterday and none of the suggested resets have worked. This morning i tried to call to get a replacement and after more than 30 minute wait I get some idiot guy who claims the line is too crackly to hear me, despite me having perfect signal. He kept claiming he could barely hear me, then promised he would call me back immediately on the number I was using.

Obviously there was no call back. The reason I think this is a scam where these idiots just don't want to do their job is this is now the 3rd time this has happened to me over the years of having to call virgin media. With 3 different phones and 3 different network providers. It's also the only times I've ever been told by someone on the other end of my phone that they can't hear me.

Who else has experienced this? It clearly seems to be a well known and used tactic by the more useless call staff who can't be bothered to do their job.