If it is a special offer, such as cashbacks, discounts etc, these will be subject of the T&Cs of the offer, and will sit outside the banking code. Offers may have conditions which state the offer can be terminated or changed at the discretion of the business making the offer.
What do the T&Cs for the cashback say in relation to the offer’s termination?
That is a very common inclusion in offers, give-aways, lotteries, etc, etc. It gives businesses an out if they feel that there is something fishy happening, or all the stocks of the give-away/promo item are exhaused etc.