Insufficient funds

I was suprised to receive an email from a representative from Melbourne University regarding the acceptance form.According to them,the credit card has come out with insufficient funds.How could this incident is happening now?They should hv informed me earlier.Now,it delays everything from eCoE,visa application,medical checkup and so forth.I should hv checked the inbox this morning and it can settle this problem by this evening.It's too late already.Really hope it can settle by tomorrow or on Friday.Or else i hv to make a bank draft or the Telegrapic Transfer(TT) to the university which it will take times for them to receive the payment.Why everything is happening in the last minute?