Accidentally deleted my phone app

You cannot actually delete the phone app. You probably just removed it from the home page. You can find it in the app library. The app library is found on the page after the last page of apps (keep swiping to the right). Try to find the phone app. Hold it and drag it to the position you want. Hope you find this helpful!

Really glad that it worked for you :)

This is my first accepted answer. Pretty happy about that!!