If your bill is overdue for the first time, you will get a reminder, if you still don't pay within the date on the reminder, your line will be cut off.
If you just leave it there and forget it, the charge will be deducted from your S$200 deposit. If you did not pay a deposit, you will be sued.
If you don't want the above situation to happen, you need to pay the bill and extra S$20 reconnection fee.