Mobily

So I go into my local O2 shop to buy a new mobile phone.
"Hello," I say to the man in there, "I'd like to buy a new mobile phone please."
He looks at me as if I'm talking a foreign language. "Ok," he says hesitantly, "what sort are you looking for?"
"A cheap one, " I say, "pay as you go."
"Uh huh," he replies slowly, "and a Sim card?"
"No, no," I say. "Just a new handset." I don't want a new Sim card: I've only just managed to memorise my mobile phone number!
He breathes in through his teeth. "Well, have you got your old phone?"
"No," I tell him. My old phone is lying on top of my printer at home.
"You see, I need to check the Sim card before I can let you have a new phone."
I'm slightly confused by this. "It's O2," I say, thinking he's got the wrong end of the stick.
He nods slowly. "Sure," he says. "But is it compatible?"
What?
"Erm, should be," I say.
"See, I can't let you buy a new phone until I'm sure your old Sim card is compatible. I can let you have a new phone and a new card; then you could have 300 free texts!" He grins at me; I half-expect his teeth to go ding and flash.
"I just want to buy a new phone," I say, feeling very muddled now.
"With a new card?" he asks, still grinning.
"No, just a new handset," I say.
His smile drops. "Can't do that until I've checked the old Sim card."
I take a deep breath and count to three. "Okay," I say, "I'll come back later with my old phone."
"Good, I'll be here all day," he tells me.
"Wonderful," I say, a huge fake smile on my chops. "Thank you for your help, good bye."
I'm out of there quicker than a rabbit on steroids.

Why is it so difficult to buy a new phone these days? I appreciate that technology may have moved on, bu my Sim card is only (just about) three years old! I shall try again later on in the week.

Laters.