Really?
I am not making a sweeping generalisation about any of the accents that will follow, but...
When I used to call A&L I would get a scouser, always very nice, but sometimes damned near impossible to understand. Similarly, when I call Sky I get a Geordie (not so bad on the whole), or a Scot which is a lottery since the accent is either very heavy or not. There is another company, which I cannot name here, which has its call centre operations out-sourced to a company in Cardiff, and a lot of the time I cant understand them either....which is amusing since I lived up that way for years.
Face to face I have no issues so I can only assume that accents+telephones='Can you repeat that please'.