Since there are terms involved in a commercial transaction, that - in and of itself - constitutes a contract or agreement (of the terms) between the merchant and R'osity in exchange for hosting the products. Therefore, neither side could change the terms of the agreement after they have been agreed upon without offering the other party the chance to read and agree to the new terms. All agreements are "set in stone" once both parties agree until such time as both parties acknowledge and accept the changes. It would appear that R'osity is, once again, trying to use linguistics to absolve themselves from a fix they placed themselves in. IMHO, I do not see the pertinence as to whether you call it an agreement, a contract, terms of service, etc; they all imply the same outcome.