it matters when you say 'la'

i was at SS2 wai sek kai wondering round for food at 11++pm last week. bumped into my fav drink stall 'bubble tea'. as usual i'll order the green apple bubble tea.
knowing that my cantonese is bad...i ordered. the kind man replied me in cantonese...telling me that they ran out of 'pearls'. then i replied...'mo siong kon' in a sad way (telling him that i don't want the drink).

minutes later, a gal holding the drink was going round asking every patron whether they have ordered the green apple bubble tea. i was wondering if that was the drink that i've ordered. she came towards me and i said 'no'.

minutes again later, the man was going around instead. when he spotted me, he came directly to me. deep shit! he looked at me...i looked at him. he handed me the drink. i told him directly in ENGLISH, 'uncle, i told you i don't want that drink'. he looked at me furiously and walked away.

hahns asked me whether i told him correctly that i didn't want the drink. i told him i said 'mo siong kon' to the man. then he asked did i added the 'LA' behind. i said i didn't.
well, if i had said 'mo siong kon LA' then he would have known. shit...

i headed home feeling guilty as ever and wondered if he remembers me the next time i order from him again...