Need help my iPhone won’t download GarageBand

Whenever I try to download GarageBand app on my iPhone 6s Plus it only downloads the app like I offloaded it and I click it to download it and it says it requires 17 ios update and my iPhone won’t update that far so why can’t I download an older version of it but my iPhone won’t let me and it’s making me really really upset because I feel like stomping my phone