i had been finishing my college education in nebraska with plans of moving to australia once i had finished school and met the necessary immigration requirements. during the summer, on my yearly visit to friends in australia, one of them unexpectedly offered me a job. i remained in the country and we applied for an immigration business visa but the processing time was over 4 months. during this time i wasn't legally allowed to work and fell behind on credit card payments. my biggest mistake was thinking that i could make up a couple of missed payments, but more time passed than i expected and here i am, 5 months past due and in another time zone (+10 GMT).
this morning (5am saturday for me & 10am friday in california) i received a phone call from a lady at a collection agency informing me i have defaulted on my account and that i have till monday to pay the full amount of $5800 or she would have to advise the credit card to take action. i can't remember which agency she said she was with because i was half asleep when she introduced herself, but i do remember her saying that they didn't purchase my debt from the credit card. she didn't give me any details on how, who or where to pay, but she gave me her name and a number to call after 9am california time tomorrow.
what options do i have if i can't pay the full amount? how am i supposed to handle possible lawsuits? should i get a lawyer? if so, from which country? i also read that i'm supposed to request the collection agency to validate the debt. i haven't received any letters from them yet, but am going to be expecting one now that they have my overseas contact information. how do i request them to validate my debt if they're telling me i have to pay by monday?
this is the first time i've been in any kind of trouble and i'm feeling a bit overwhelmed about what to do and who to contact. any advice will be greatly appreciated!

