I don't know about flybe but many airlines permit mobile phones to be switched on during the flight as long as they have been switched to flight mode (they still need to be switched off for take-off and landing).
Unfortunately, there is no way for cabin crew to tell easily if the phone is on flight mode or not and if there is no specific reason there is no way how crew could check every phone.
I personally disagree with the policy and think they should be all switched off. Makes it easier and safer for everyone. But I'm not making these decisions so the only thing left to do is to only check if I spot or hear something that gives me an idea that the phone might be not in flight mode.