If a train is replatformed, the station has changed which platform it will use. You were told to wait at one place, but now you must go to a different part of the station to get on. This is mainly British English. You hear it in announcements and on the boards: “This service has been replatformed.” Ordinary people almost never use it at home. The subject is usually the train, not the passenger: the train is replatformed; you just walk. Staff can also replatform a train, meaning they move it to another platform. Though actually, computer people use the same spelling for moving software onto a new system — that is a different job for the word. Here it is only the station meaning. It often happens late, so people run, and they can sound annoyed because the tidy first instruction was not the last one.

改月台、更換月台。台灣車站說「月台」（不是「站台」），廣播常說月台變更。