Phone calls that are 'suss'.

I just had another phone call when the caller failed to identify themselves or their organization, and asked to speak to Susan. This is the bane of my life.
Conversation went something like this:-

Ring, ring, Me:- 'Hullo'
She:-, 'Hullo, could I speak to Susan please?'
Me:- 'Which Susan would that be?'
She:- 'Susan H.'
Me:- Yes, that is me. Who is calling please?
She:- My name is Helen. I am calling about a membership you had with us.
Me:- Who do you represent?
She waffle.
Me:- I am sorry but you have not told me who you represent. What organization are you from?
She:- Oh, I can't tell you that, it is a privacy thing.
Me:- If you can't tell me that, then I can't help you.
She:- There is not need to shout!
I hung up at this juncture.
This call was on my mobile and the number was withheld.
I am soooo sick of people ringing me no matter which phone they call me on, who just ask to speak to Susan. THEY get stroppy when I try to make them tell me the full name of the person they wish to speak to. It is just good manners to aprise the callee who is calling.