Heard a random man talking through my phone speaker but no phone call made

I was sat at home reading an email and suddenly a man starts whispering through my phone speaker saying ‘I ain’t leaving’ it then went quiet and I could just hear him whistling to himself??!!

no call was made???

I checked Facebook and Instagram but no videos were being played at the time.

Could this be radio interference or some sort of phone hacking?

has anyone else had a similar experience?