Handphone Shop Story

I'm here to continue the story of the handphone shop thing.
Monday night, my sis went to help me get the things from the shop.
Okay, we're supposed to get the crystal case, desktop charger, and have an exchange of the battery.
When my sis got there and told the guy about the battery,
she said he looked a little panicky and worried.
So anybody would have seen right through him.
And they actually didn't get the stocks for the crystal case,
when he told me last week they'd get them by Monday.
So my gungho sis showed him a black face and probably said something nasty,
which sent him scurrying to another handphone shop to borrow a crystal case first.
Then my sis came home, with an air of triumph.

The thing that infuriates me the most is,
they obviously want to cheat people of the battery right?
Why can't they be more professional about it?
That guy told me on the phone last week,
"There may have been a mistake,
I might have given you the wrong battery 'accidentally'."
So shouldn't he be treating the whole incident as an accident?
Instead of clearly showing it on his face?
I think the only thing I've got to say is...
He's only recently started working there.
Or maybe I'm the only customer he's had that didn't fall into his trap.