Anyone know how to cancel free 3 month trial subscription with Apple tv?

I received an e-mail from roku with offer to purchase a roku ultra, and receive a free 3 month trial subscription to Apple tv on my roku. I purchased the roku ultra, followed the directions for the 3 month free trial subscription, and started receiving apple tv on my roku. P:roblem is I do not like anything apple tv offers; so I asked roku how to cancel the trial subscription, but they indicated it has to be apple tv since the trial subscription is with them. I contacted apple tv via chat and after 3 hours of runaround, I got nowhere. Question is, has anyone tried to can with apple tv, and if so, how do I cancel the trial offer? Both roku and apple tv say they have no record of it. That's great, but after the 3months of free apple tv, I will start being billed for something I don't want. Anyone who has a solution, please let me know. Thanks.