If Wi-Fi Calling appears to be blocking calls, the first thing that you want to do is to restart the Wi-Fi Calling apps. Refreshing an app this way sometimes fix minor bugs. To check if the problem is temporary, follow these steps to restart the said app.
On your screen, tap the Recent Apps soft key (the one with three vertical lines on the left of the Home button).Once the Recent Apps screen is shown, swipe left or right to look for the Instagram app. It should be here if you managed to run it previously. Then, swipe up on the app to close it. This should force close it. If it’s not there, simply tap the Close All app to also restart all apps.