How to disable Background App Refresh on iPhone
Step 1: Open the Settings application on your iPhone.

Step 2: Now, in the Settings app, tap on the “General” option.

Step 3: Tap on the “Background App Refresh” option.

Step 4: You will now see settings related to App Refresh. You can disable Background App Refresh on an app-by-app basis here. Just tap the switch beside each app you’d like to disable to turn it off.

Step 5: To completely disable Background App Refresh for all the applications, tap on the “Background App Refresh” at the top of the page and select “Off” from the list.
It’s noteworthy that the Background App Refresh feature gets disabled when you enable Low Power Mode on your iPhone.