How exactly does the pay-as-you-go plan bill me?

Per order, not per month: each day the platform counts your orders — including cancelled ones, stated up front — at your plan's per-order rate, and the balance grows until it reaches the charge threshold (AED 10 by default), when your saved card is charged with 5% VAT on top and a receipt follows immediately. Your billing page (Settings → Plan & billing) shows the running balance, every counted day with a link to your own Orders board for that date so you can verify the count yourself, and every charge with its exact days. Card statements read GETMENU.AE. A failed payment is retried, carried into the next invoice (never billed twice), and you can always settle by bank transfer instead.