When using OneStepCheckout.com (and other extensions) with WebShopApps there may be occasions when you see problems around shipping that are related to the checkout extension as opposed to the WebShopApps extension itself.
Below we outline some of the issues we have seen.
Shipping Rates being shown in checkout when no Address Entered
This is quite a common issue of the rates being shown before the full address of the customer has been entered. This can then lead to the incorrect rates being shown at the checkout stage of the store.
A way to confirm the issue is to disable the OneStepCheckout extension from the store and use the default Magento OnePageCheckout. If the rates are then displayed as desired, we would suggest discussing the issue with the developers of the checkout extension.
Being able to Checkout with no Shipping Rates
This is always a problem with your checkout extension. The WSA shipping extensions do not control this, they just respond to requests for Shipping Rates