I work for a major UK charter airline. Our Civil Aviation Authority have stated that phones that have a "flight mode" may be used on board an aircraft, however this means that Cabin Crew will have to become experts in which phone has this mode. With this in mind they suggest a total ban. My airline has followed this guidline and makes the following PA
"Whilst on board this aircraft the use of mobile phones including those with flight mode is prohibitied"
Hope this helps