Shipping Rates Don’t Match FedEx Account

First off I like the plugin so far. Not sure if your team is looking for people to contribute to your project but I’d be interested. The woocommerce options for FedEx are limited and this project is very useful for us. The only issue I am running into is that the shipping rates are not matching what I see in our FedEx.com account. Typically the rates from the API are too low but not always. I have used the filter you provided to add to the rates. What causes this? The rates appear to be cached. Your help is greatly appreciated. Keep up the good work.