Back in the UK I was waiting to buy a spare part for my car when the phone rang and there were two people still in front of me, the assistant left the person he was about to serve, answered the phone, then put it back on the counter and walked away, presumedly to go and see if he had what the caller wanted. I immediately walked up and pressed the phone cradle to cut it off then walked back behind the two people in front of me.
I just think it is unfair that people always seem to get preference and can jump the queue just because they are on the phone.