Hi Kathleen and Ian :) You found one entry because you searched for Gionis, with the g pronounced like the greek gamma. My guess is that the name is spelled Gkionis. There are too many entries in the area of Athens, but there are only 6 entries in the area around Marathon (in www.whitepages.gr you choose attiki as region and rafina as town). One of them is called Nico, working for the greek phone company and his number is +30 2294023758. Could he be the one in question?