I'll do this in an conversation type of text. Hopefully this will be okay to follow.

Customer : Are you closed?

Me : I closed ten minutes ago and getting ready to go home.

Customer : I need some gas on my key, can you not do that for me?

Me : Okay that's fine but it's cash only, I no longer have my till out.

Customer : The cash machine isn't working. Can't you just put do it for me an favour?

Me : No because I'll be out of pocket, plus I have never met you before.

Customer : Its so cold can't you just do this for me?

Me : I'll wait for you to go the cash machine, you draw the money out, then I'll put it on your card.

Customer : Why should I do that when you can just put it on now and then I pay you later?

Me : As I explained to you lady, I'll be out of pocket.

Customer : I'm only asking for £20 on my gas key, why you been so fucking difficult?

Me : Okay. I was happy to wait till you got some money out of an cas-

Customer : You're an fucking prick! You wasted my time when I could of gone and got it elsewhere! What's your name so I can report you? Well, what is it?

Me : Yeah my na-

Customer : I don't understand why you can't do such an little thing for an customer and won't tell me your name. Fuck you! I'll speak to your manager!

Customer walks off... I sit in the back, for a little bit thinking... What the actual hell did I do wrong apart from trying to be nice?