sadly as mentioned above, samsung safeguarded it by stating clearly everywhere its a promotional offer ending on the 25th regardless of circumstances or accidents on websites.
only exceptions are order confirmations on or before the 25th that have been cancelled by a retailer because of an error, low stock or otherwise where a new order had to be placed for an example.
a few people has mentioned speaking to Samsung CS and both came on the forum independently region wise and said Samsung will be running another promotion later in March on the S21U.
what kind, what deal or item(s) I can't say.
if you can wait up to a month you can return or cancel yours but it could be nothing happens.
if you are in the UK, that deal literally ran across all Samsung services and carries with contracts or outright purchases.
some like EE still give you the Xbox (Razer Kishi) controller and 12 months for xbox live free IF you are buying it outright with a pay monthly plan or signing a contract for 2 years. at around 20 to 105 pounds depending on your choice and or down-payment.
there's still SOME choices for ya