Google Pay for India (aka Tez) app for iOS is not available for download through Apple App Store for some time. The app is missing from the App Store and users are instead provided with few of its competitors including PhonePe and Paytm when particularly searching for Google Pay from India.

source https://gadgets.ndtv.com/apps/news/google-pay-india-tez-ios-app-unavailable-apple-app-store-download-payment-failure-issue-2315852#rss-gadgets-all