A good invigilator would tell you to be quieter after you uttered the first word...I would also point out that even having a phone on your person (even if it was switched off) would be reported to the exam board and would likely result not only in you being disqualified from that one exam, but also risk you being disqualified from ALL your summer exams and for 3 years after the event, you would be blacklisted meaning any other exams (at college or university) you could be disqualified from too.
Invigialtors escort candidates to toilets - at our school they would usually open the door of the cubicle before letting to candidate in - really not worth the risk.
If your phone is in your bag, and your bag is in the exam hall this is also considered a major violation, resulting in the same penalty. Exam boards are now saying that if someone says they have not got a phone, so have not handed it in, if they are then observed later that day with their phone, the school can inform them - they take it very seriously - it really isn't worth cheating. Invigilators see words written on hands, arms, rubbers and will make you wipe them off, record it, inform the exams officer who will tell the exam board - cheaters are taken a very dim view of by schools, invigilators and exam boards....