There is nothing as such in Qatar Labor Law for banning Cell Phones in workplace. But Company's internal policy can ban its "excessive" use during working hours, provided that you give solid reasons for the ban.Its very difficult to monitor the use of cell phones, hence nowadays smart phones are available which itself has all functions which can give worker options to play around and kill time during working hours. You should not ban fully the cell phone, but in fact should circulate a policy banning the use of skype, watsapp, viber, fb, internet surfing, excessive calls etc etc on smart phones during working hours. If you catch anyone violating the policy , take strict action so others can learn from it, it will make lil difference. (During lunch hour, let them do whatever they want to do but not within working hours). One more idea, install cell phone signal jammers in office vicinity, it will automatically help you ;)