From what I can see on the internet here in the UK the CAA view the mobile phone as a personal electronic device (PED) that causes interference with aircraft electronics systems. Consequently its use is restricted to aircraft on the ground at the operator’s discretion unless the aircraft has a specific exemption.
I dont know the details, but AFAIA, there is a current study into the use of mobile phones being used whilst airborne. When I flew with a guy a few months back in the primitively instrumented C172, his mobile phone signals had nil effect. Also I know of pilots texting family whilst on an ILS with nil effect also.