If all you hear are strange, muffled noises, chances are it’s a butt call.
butt call
/ ˈbʌt kɔl / nounan informal word for a call that you make by pressing your phone by accident:
It must be a butt call – I can’t understand a thing.The verb is butt-dial or butt-call:
It can be embarrassing if you butt-dial your boss from the bar.Read all about it: Will smartphones take over the world?