Some people just can't say it right...

Usually when a customer came to the shop for a top up,especially the students,they'd say,"top up saya".
One customer came and just said,"ada mas-is",or something like that.So I said,"oh,tiada,kami tidak jual mancis."I said that because we don't sell matches at the shop.He gave me a stare as if to say,"is this lady daft,dim witted or just plain deaf?"
My friend said,"kak,maybe he wants to top up his maxis",and sure enough that was what he wanted.But why didn't he say up front that he needed a top up?
When the customer left we both doubled up laughing.My friend said that she too heard mas-is but she thought of maxis and got it right.I heard mas-is and automatically thought of matches.