The Call Is Coming From Inside The Phone!

I go to my friend’s place, and he seems to be flustered. He’s walking around trying to make a call on a cell phone.

Me: “What’s wrong?”

Friend: “I can’t find my phone!”

Me: “So you’re trying to call it to hear it ring?”

Friend: “Yeah, but every time I try to call my number, it doesn’t go through! It’s not working!”

Me: “Wouldn’t it be funny if you were trying to call your phone from your phone?”

Friend: “…” 

He stops the call, looks at the phone, sighs deeply, and then looks back at me.

Friend: “In my defence, I was up all night studying…”