You need an app for your phone which can record wav files. Here are some suggestions.
The first is Dolby On.
Google Play Store: https://play.google.com/store/apps/details?id=com.dolby.dolby234&hl=en&gl=US
Apple App Store: https://apps.apple.com/in/app/dolby-on-record-audio-video/id1443964192
basic advice on recording audio with a phone: https://www.conquerthedigitalempire.com/blog-all/improve-audio-recorded-on-a-smartphone