Refund on app that does not function as advertised

Hello.

I purchased 2 in-app items expecting them to work as described. The app/game is Bricks n Balls from Cheetah Technology Corporation Limited.

One was a "remove ads" feature, another was a gameplay feature. Even after purchasing the "remove ads" feature, it still shows ads for other 3rd party games. They are 30 or 60 second ads that cannot be skipped. The gameplay feature still doesn't work.

To rule out instal issues, I uninstalled the game and reinstalled it. In the game, both items show as "purchased", but neither function.

In game, the company provides a link to ask questions for support. They chose not to reply to my emails, but issued a product update that included the words "Golden Aim, is available and working", so apparently I'm not the only person complaining about this broken feature.

How do I get a refund for these two purchases?

Thanks