Joke for Pizza Delivery

I ordered a pizza delivery half an hour ago...

(20 minutes later.....)

"Ding Dong~"...The delivery came so as my pizza....

Delivery Man: Hello sir...I'm here for sending the pizza that you've ordered..

Me: Hi...

Delivery Man: Let me make a confirmation...You've ordered a XXX pizza....

Me: Yeap,correct...

(He pass me the pizza)

Me: Thanks....So how much is the total?

(He look at an unknown sticker on his shirt)

Delivery Man: Oh...Is total RMXX sir..

(I give him a RM50 and 80 cents)

Delivery Man: Thank you sir...

(He silence for few minutes while I'm thinking why he still haven't give back me the change)

Delivery Man: Hehehehe....(laugh lightly with full of embarrassment)

Me: Yes?

Delivery Man: How much is the change that I should give back you sir? Hehe....

Me: ..................................(My God..=.=)

Me: Is a total RMXX...(If I'm bad I would say RM100....)

(He gave me the money and leave)

I'm wondering what's the requirement for being a delivery man...^^