You all know the actual reality of electronic devices interfering with aircraft systems is
right?
Avionics in commercial airliners are heavily shielded for a start, there have also been nuemrous ground test which have never attributed any interference with flight instrumentation or systems due to mobile phones etc... (there was one test which showed a marginal effect on an ILS instrument but this phone was IN the cockpit)
There has never been a single incident attributed to electronic interference with in flight systems from within the A/C
In short your mobile phone will not turn of the autopilot!
Most FA's have a great deal of training etc etc... but on the technical details of aircraft and aircraft systems they aren't experts and are most likely perpetuating the myths they learnt in training.
I have use a mobile phone while in the cockpit on several occaions and i didn't end up upside down!!!