Do aircraft really have text communication over FMC?
Yes. Text messaging over ACARS has been commonplace since the 1980s. It is air-to-ground and ground-to-air, not air-to-air. It is commonly used to exchange flight plans, weight and balance data, ATC clearances, schedule updates for passengers' connecting flights, and other operational purposes, but also sometimes for fun (e.g
birthday wishes, sports game results). It's primarily used between an aircraft and the airline's dispatching department, but can also be used directly between the pilots and ATC under some circumstances.