GTA 5 Online Refund Request Denied by PlayStation Store

Yesterday, I purchased GTA 5 Online from the PlayStation Store. Today, the game was downloaded and installed. However, when I tried to open it, I could not enter the online mode. The game informed me that without a PSN Plus subscription, I cannot access GTA Online, and that I only own the story mode. I would like to request a refund, but my refund request has been rejected. I am asking for the purchase to be canceled and refunded.