2/7/22 update: Nowadays, Walmart no longer gives you the chance to reject substitutions online or through the app. Repeatedly, the order is stuck in Preparing status, which means it's being picked. But at the same time, the app says the window to reject substitutions has expired. Then minutes later, and only 20 minutes before pickup, I receive a text message indicating that Walmart is ready for me to reject substitutions. But when I log in immediately, the app still tells me I can't do that.