Fix bug on zen cart shipping module

I have a zen cart shipping module that uses the Australia Post API to get valid shipping quotes. The module works properly at step 1. It displays the shipping options and the price with radio selection buttons. Here is a picture of step 1 of the checkout process: [login to view URL] The problem occurs at step 2. When I choose an available shipping option in step 1, the shipping cost on the next page always shows the most expensive shipping option. Here is an image showing step 2: [login to view URL] The problem is that even though I selected the regular parcel in step 1, at step 2 the shipping method shows as platinum parcel. Can anyone debug this for me. I can provide a copy of the script and ftp access to a zen cart test site if you require it. Thanks.