Chop Chop Chop-Stamp Stamp Stamp

If you watch "Oh My English" you'll know what's wrong with the picture above. If you didn't watch before then you click and play the video below there.
Last night I went to Yayasan and I spotted this sign in front their shop.
What you can say??? We are a multicultural Chop kah... Stamp kah.... as long as you understand I understand Ok sudah lah!!!
But think about, Chinese call Chop, Malay also call Chop only English call Stamp... Why call Stamp? I'm not posting letter ma... If I need a stamp to sent letter then I stamp lah.
Eh..... if cannot call chop must call stamp then what do you call the stamp on the letter that already use? chop right??? "Stamp the Stamp before you send the letter with the stamp on the stamp" like that kah??? hahahahah