I pay the full amount for Roku TV and is not working it's not letting me subscribe to it so what can I do or how can I get my money refund
What do you mean by "Roku TV?"
After you purchase the Roku device, there is no fee to use Roku itself or the Roku channel. Many (most I think) channels have no fees either. Although some specific channels like Netflix, Prime Video etc. do have their own fees.