ATHENS, Greece — Crowds of anxious elderly Greeks thronged banks for hours from before dawn Wednesday, struggling to be allowed to withdraw their maximum of 120 euros ($134) for the week, after Greece reopened some banks to help pensioners who don’t have bank cards. The often chaotic scenes came hours after Greece’s bailout program with European creditors expired and it failed to repay a debt to the International Monetary Fund, the first developed country to do so.