You cannot use a mobile phone during the exam session.  Doing so will result in the termination of your exam.  Plan to be unreachable via phone and keep the phone away from you while taking the exam.  The only time you can use the phone is to sort out the technical issue if the proctor cannot reach you via chat and VoIP. It is probably a good idea to avoid using your phone during the break if possible so you are not distracted by work and family. Rest assured that the world won't fall apart by delaying the text or email for another 2 hours.