My pdoc's phone goes off more sessions than not. Sometimes he declines the call, often he answers saying 'I'm in session right now, I'll call you back/stop by after x' (stop by if it's the ward calling), and very rarely he's on the phone for more than a few seconds. Today he actually walked out for a few minutes to answer the call.
I don't really mind. I get the feeling he always declines calls if I'm very upset, and today I was borderline upset and he was very apologetic that he had to take this call. And there have been times he turns off his phone after it went off.
You know, the fact that he's sometimes late and he sometimes takes calls in sessions means two things: that he's willing to go over time and fit you in for an emergency appointment if necessary, and also that I can reach him if necessary (through the office - I do have his cell 'by accident ' but I'd never call him on it).

For my T, it bothers me more. Also because last session she 'had to take this call because it was about tomorrow' and then she spent a few minutes talking about a presentation that she had to give tomorrow whereof the PowerPoint was lost or something. But that was settled in the first 30 seconds and then she spent a few minutes talking about non urgent things concerning that presentation ('I was so worried' 'I am so relieved' 'I looked everywhere'.). Fine if you want to talk about that, but do it outside my session time, please.