What do you do if you were me?

well i worked in this particular company, it's a retail company .. and a big company too. i work as a sales assistant. somehow i made a mistake by a shortage at a cashier. well now i wanna quit my job. because it just doesn't suit me and also the people there just like to bully people. though me as a first timer they shouldn't shout at me. and now i wanna quit like right now, they say if i quit now no salary for me all will be gone.. so they tell me to work for 3 more days but i just can't stand the ppl there and all the work i did. and the bully i got. so what do you do to fight for the pay that you want ? i've been working there for 17 days. but yet they should still give me my pay right ? i worked really hard. actually most of the jobs i did were the hardest ones. and me as a first timer they should assist me not leave me alone just like that and handle the cashier. so what do you do to get your salary even if you didn't go to work for that 3 days notice ? help me ... thank you...