1. KNOTS LANDING - A Phony Call From Ben



After phony messages on an answering machine, Jill decides to up the ante with a "live" conversation. It's just a snippet so the phonecall only lasts a few moments.
But then Valene, totally confused and over-excited, calls the operator in order to trace the call.
"My husband just called me from South America!"
When Jill leaves we can still hear Valene's hysterical voice, accompanied by a very eerie version of Mockin' Bird Hill, which makes the public phone look like an evil jukebox.
2. THE COLBYS - A Phony Disconnection

To cut a long story short: Fallon is pregnant, in the mountains, in pain and needs a doctor a.s.a.p.
Channing feels her happiness is being overshadowed by Fallon's baby, so when she offers to help and calls a doctor, she pretends that she can't hear him.
"Hello? Can you hear me? This is an emergency!"
-"Yes I can hear you, but can you hear me?"
Channing hangs up.
"The line is completely dead. Oh my god, Fallon, what are we going to do?"
3. DALLAS - J.R. Calls The Shots

"Dad? Dad!"
Interestingly, this phone conversation was completely staged (for obvious reasons) so they sort of did it like Jill did with Ben Gibson's voice.
4. DALLAS - Mistaken Identity

Christopher discovers that the other person on the phone is not his wife, and the woman who's not his wife discovers that the other person on the phone is not her brother.
5. THE YELLOW ROSE - Beyond The Call Of Duty

Caryn Carbrera, the personal assistant of evil Jeb Hollister, betrayes her employer when she calls his estranged sister to tell her that her brother might die.
To make sure that the estranged sister is interested, she tells her that Jeb's daughter is romantically involved with Roy Champion, Jeb's nemesis, and if that merger goes through they will control both empires.
Caryn reminds the estranged sister that the estranged sister's son, fathered by Roy Champion's father, is both a Champion and a Hollister, and therefore deserves to inherit it all.
Caryn's motive isn't very clear but there's a lot of soap in that single phone call.