Answer:
As the scene begins, Mrs. Stevenson is feeling irritated and also fustrated because she is unable to reach the number she was dialing- actually her husband's office line.
We know this because in her fustration and irritation, she slams down the phone.
Below is an excerpt from the text that explains her condition:
Mrs. Stevenson is dialing a number on the phone as the curtain rises. She listens to the phone, slams down the receiver in irritation... She reaches for her pill bottle, pours herself a glass of water, shakes out a pill, swallows it, then reaches for the phone again, dials the number nervously.
Explanation:
"Sorry, Wrong Number" is a play written by Lucille Fletcher.
It tells the story of a murder case which was planned by the husband of Mrs. Stevenson which was unknown to Mrs. Stevenson. Mrs. Stevenson overheard the conversation of the murderers but never knew she was to be the victim. She tried her possible best to stop the unknown victim from being murdered.