No.
And neither was Carpenter's HALLOWEEN as frequently claimed.
And Darkness and Decay and the Red Death held illimitable dominion over all.

Wasn't this film supposed to have been the sequel of Black Christmas?
I Love Debi Sue Voorhees
http://s32.postimg.org/btmfhyrk3/Debi_Sue_1.gif

Both THE NIGHT GOD SCREAMED and BLACK CHRISTMAS did the threatening calls/killer lurking in the house routine years before WHEN A STRANGER CALLS.
In fact, THE NIGHT GOD SCREAMED even featured a masked, cloaked assailant brandishing a knife and chasing a victim in the garden very much as we saw in SCREAM.
The main difference is it wasn't at the opening..but that wouldn't stop it from being an inspiration.
And Darkness and Decay and the Red Death held illimitable dominion over all.

The entire opening of the film was about nods to horror movies. They didn't steal it. They were paying homage.

Yes it did steal it..and very poorly.

I've never heard them (Wes Craven or Kevin Williamson) mentioned it. They mentioned Halloween and Prom Night but I don't remember they ever spoke about this one. Of course I can't remember all their interviews so I may be wrong.
But you will often find Scream mentioned in reviews of When a Stranger Calls, not the opposite. So is it really Craven and Williamson who said it was a homage or is it the reviewers who kindly assume it is?

www.1up-games.com
Last seen:

Scream's opening is actually a direct homage to this movie

It is strange how this film is never referenced openly by any of the characters at any point. True, nobody knows the exact events of the first scene with Drew Barrymore apart from the killers, but it would've been nice to see them mention it to Sid in the final act or something (even in passing). They surely must have been influenced by it (and by extension, Wes Craven too).
Violence is Italian art and Italian art is beautiful.