The same thing happened to me. I was quoted a lower rate with the understanding that I enroll in automatic payments. Needless to say, even with auto pay I never saw the lower rate. Paid off the car in 18 months and used Chase to finance my truck. Chase's rates were lower and there was no deception. I like USAA and continue to use them, but I haven't forgotten they are a business. As a frugal consumer I continually compare with other companies.
I work at a bank other then USAA and I can tell you that your quoted rate is just a quote for a reason. They can only quote you off the standardized chart. You're actual rate is dependant upon credit, auto debit, and banking relationship. Credit and auto debit drives it. The vehicle you purchase ie new or used, also drives the rates. It was probably all listed in the terms