The Second Voice on the Phone

Last night, something strange happened while I was on a call with my friend.
We were talking about completely normal things — work, plans for the weekend, nothing unusual.
Then suddenly, in the middle of our conversation, I heard another voice.
It wasn’t an echo.
It wasn’t noise.
It was a clear whisper, like someone standing right next to the phone:
“Don’t… open… the door.”

I froze.

My friend was still talking, completely unaware.
I asked if anyone else was with him. He said no — he was alone in his room, and the door was locked.
A few seconds later, the whisper came again.
Same tone.
Same breathy sound.
Just one word this time:
“Please.”

I hung up.

This morning, my friend told me something even stranger.
He said I was the one who suddenly changed my voice last night — that I whispered something disturbing before the call ended.
But I never said a word.
So now we’re both wondering the same thing:

If neither of us whispered…

Who did?