SDCL § 54-11-9: Creation of contract between card holder and issuer.

The use of an accepted credit card or the issuance of a credit card agreement and the expiration of thirty days from the date of issuance without written notice from a card holder to cancel the account creates a binding contract between the card holder and the card issuer with reference to any accepted credit card, and any charges made with the authorization of the primary card holder.