Your TA should have told you when you booked when the final payment was due. Was your email from the TA or from Carnival?
If it's from the TA, call her tomorrow morning and ask why you weren't told the correct date (you should have paperwork showing the due date). I'm sure she won't want to lose your booking so she should work with you.
Generally, final payment is due 2 months before your sail date (it's earlier if it's a "holiday" sailing.)