Okay kiddo, have you ever been to a party or a store that is closing soon? The last call is like a reminder that you need to leave soon because it's almost time to close.
In bars and restaurants, it means that this is the last time you can order drinks or food. It's like a warning that it's almost time to go home.
It's important to listen to the last call, so you can finish any last-minute things you need to do before it's too late. Just like when Mommy or Daddy tells you it's almost bedtime, it's time to start getting ready!