Am I obligated to pay the agent's commission to a seller whose goods I refused to buy because I was not satisfied with their quality and they did not match the picture, after the seller had already paid the agent's fee?

Firstly: It is permissible to buy online if the item is described accurately, removing any ambiguity. The buyer has the right to annul the sale if the item found does not match the description. Secondly: The delivery agent's fee is the responsibility of the seller, because the seller is the one who hired him, unless the seller explicitly states to the buyer that the fee is the buyer's responsibility. If the seller sends an item that does not match the description, then the seller bears the fee because he misled the buyer.