Description:Darren Groom, 36, said he was "fed up" with people expecting him to "lip read" their order at his shop in Norwich.
He has now put up signs telling customers they will not be served while using a mobile phone.
Etiquette experts Debrett's said Mr Groom was "performing a public service".
Mr Groom, who sells coffee at his city centre shop and market stall, said the reaction to the signs had been very positive.
"We've had lots and lots of comments," he said. "People are saying how much they agree with it.
"A couple of years ago it became a real problem with people trying to lip read their order to us.
By Mark Bulstrode BBC News(1:25)