You will first want to revert this page back to it's default state before you were getting this error. Once you have it back to normal you can add in a couple of things to help you with this. The first thing that you need to add is the form data from the checkout page. To do this go to bindings > form data, in here select the checkout page. This will get the form bindings for the checkout page on your confirm page for you.
Once you have the bindings available you will want to add a set session value server behavior from Server Behaviors > eCart > General > Set Session Value. Give the session variable a meaningful name, the for the value use the lightning bolt icon to select the service type select list from the checkout form.
Finally when you modify the shipping quote server behavior you will update the service type to use this session variable that you just created. You will need to get the page back to it's default first. Then you can add the changes to the page one at a time.
