ἀντιχρηματίζομαι
From LSJ
Ζῆν οὐκ ἄξιος, ὅτῳ μηδὲ εἷς ἐστι χρηστὸς φίλος → Life is not worth living if you do not have at least one friend.
English (LSJ)
transact business instead of another, PFlor.382.59 (iii A.D.).
Spanish (DGE)
actuar en nombre de otro, representar, PMich.529ue.49 (III d.C.), cf. PFlor.382.59 (III d.C.).