How rude !
Just when you are about to start an enjoyable meal, some people decide, with absolutely no warning, to have a little chat with someone who is not at the table. If they truely believe that there is someone listening, they should really say “Excuse me, could I make a call ?”. (And it is rude to close you eyes while talking to someone anyway.)
I always pick up my iPad to Twit or make a comment on Facebook while they are mumbling. At least, there is someone at the other end.