As I understand your Post it contains two key points:
1. I assume the "Amount" you mention is the Amount Owed column shown on the My Accounts Summary - Banking Section of the USAA Website Main Page.
2. It is NORMAL for the Amount Owed value to both increase and decrease based upon your Credit Card Transactions and Payments.
3. If you are seeing a constant INCREASE in the Amount Owed despite making Payments then do the following:
4. If you still have ISSUE or a PROBLEM / COMPLAINT then click here to start the process of telling USAA all about it.
5. You can try to contact USAA about your ISSUE or a PROBLEM / COMPLAINT via their Twitter Response Form
6. You can call 1-800-531-USAA (8722) and speak to one of USAA's Member Service Representatives whom will be happy to assist you.
USAA can't begin to address your concerns until they hear from you.
I hope I have helped in some small way.
Thank you for your comment regarding your credit card. Thank you to Website Guru for a very thorough answer. If that does not solve your question, a service specialist would be in the best position to address your concern. As such, we ask that you please click here to provide us with additional detail and your member information. You can also reach a service specialist at 1-800-531-8722.