How can I get a refund for a faulty Screen Mirroring app?

I downloaded a screen mirroring for movie night with my family. I had a free one but forgot my speakers because it doesn’t give you sound unless you pay. I decided to take another but when downloaded I struggled with the app for almost an hour it kept kicking us out and refreshing lagging. I canceled it immediately and went on another free. I noticed I couldn’t upgrade apps nor my phone do I contacted customer care I was told to pay for the app they would refund me and fix my problem now they are denying my refund for an app that didn’t even work at all. I would have never paid for it if I wasn’t assured my money back

[Re-Titled by Moderator]