Juncker's exchange of messages with Alexis Tsipras came just hours before an emergency eurozone summit called after debt-stricken Greeks overwhelmingly voted 'No' to further austerity measures in a referendum at the weekend.
"Stop all this chatter about me looking at my telephone all the time. I am texting, as they say in Franglais, with the Greek prime minister," a clearly irritated Juncker, speaking in French, told the European Parliament in Strasbourg.
Former Luxembourg premier Juncker was heckled by several MEPs, including members of the eurosceptic UK Independence Party who had placed Union Jack flags on their desks, over his handling of the Greek crisis.
For months Juncker was the link man with leftist premier Tsipras, but after a series of late-night meetings and chummy photo opportunities produced no bailout deal, Juncker said last week he felt "betrayed" by the calling of the referendum.