You haven’t paid it back since the beginning of 2011? So basically they have already blacklisted you.
You can call POSB customer service and ask them how much you owe. The credit card interest is 24% per year and the late payment fee is 5% per month. Then I estimate that you will have to pay more than 1,000 Singapore dollars now. Bar. If you really want to repay the money, you can send money to your friends in Singapore and ask them to pay it back for you, or you can buy a cashier's check in the mainland and then send it a POSB.