In Islam, the difference between a loan and a sale is significant, primarily due to the prohibition of Riba in transactions. Loans are intended as charitable acts meant to help others without expecting profit, while sales involve the exchange of goods or wealth.

If the marketing service asked about is based on the customer or purchaser subscribing to something, meaning that he pays a sum of money in return for getting some discount or reduction in prices of goods or services that the seller is offering, then this is a haram transaction. If the transaction is haram, then it is also haram for you to tell people about it or to help people deal with it. For more information, please see the long answer.