People who phone the wrong number and then actually argue with you about it.

*Phone Rings*

Allo?
ROSIE? Is that you Rose? It’s me, Janice.
No, sorry. I think you’ve got the wrong number.
Oh, have I dear?
Yeah, there’s no Rosie here.
You sure, dear? Hang on, let me get the piece of paper…

[What's that got to do with anything? I am not Rosie, surely that is sufficient?]

You there, dear?
Yes.
See, it says here I want: *reads out number painfully slowly*

[*Groan* I know what bloody number you rang, love. IT WAS MINE.]

Is that you, is it?
Yeah, that’s me. But, I’m not Rosie.
Oh, well that’s the number it says to ring. *indignant*

[Alright, fair enough, you've got me... Rosie is here, she's hiding in the cupboard under the stairs and has just put me on the blower to sabotage her calls because you're really getting on her pip. Silly me. Hang on, I'll just go get her, sorry for the trouble.]

No, sorry-
That’s very strange because that’s the number I’ve got written here.

[Janice then calls out to someone else in the room: "Here, Mavis. This isn't the right number!" You can hear Mavis in the background: "Ohh!" Like - gasp- the scandal!]

Well, I’m afraid I’m not Rosie. Maybe the number’s written down wrong?
Hmmm… So this definitely isn’t the number I want then, dear?
No, I’m sorry.
Oh… Alright then, dear. Sorry about that.

For. Crying. Out. Loud.