I purchased Uncharted-4 Free game from PS Store on April 28th, 2020. I got billed full amount even though it's free. I don't have PS+ account. Will I get a refund? I haven't downloaded the game yet on my PS4.
I dont have PSpLus account.
That's the problem. Uncharted 4 is not free, it has become a PS Plus game for April 2020.
In other words, it's free for any PS Plus subscriber that redeemed the game in April 2020, and as long as they pay for PS Plus.
At this point, the only thing you can do is contact Sony and explain your situation to them. There is no guarantee they'll give you a refund, however.
Due to some recent comment, I'm beginning to see the bigger picture. There's been a misunderstanding on which game is currently free.
Explaining the misunderstanding to Sony may improve your chances at getting a refund, but again, there is no guarantee they'll give you one.
Since you haven't downloaded the game yet, you should be able to get a refund:
Refunds for Games, DLC, Add-ons
After purchasing this type of content through PlayStation™Store, you have 14 days from purchase to request a refund to your payment method on PlayStation™Network. If you started to download or stream the purchased content you are not eligible for a refund unless the content is faulty.