Jimmy Young's sister does all those 'phone calls

Another one... One of the other 'phones is ringing so like the good boy that I am I pick it up. It's a call for Mary. sigh...

"I've a 'phone call for you Mary."

"Who is it?"

"Mary Forbush."

"Why's Mary Forbush ringing your number?"

"She isn't I picked the call up. She rang your number."

"My 'phone's through to Betty."

"Betty's on her lunch."

"What does Mary want?"

"If you want to take her call to find out she's on my line now."

I don't know how Betty and Noreen don't run screaming from the office.